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Application Laboratory

Seminar Schedule

49th APL Open Forum

Date & Time:
21 December, Friday, 14:00-15:30
Place:
Meeting Room 1+2, 2nd floor, Conference Building, Yokohama Institute
Speaker:
Akira Yamazaki
Title:
Mechanism and predictability study of summertime Euro-Russian blocking in 2010 using an ensemble AGCM simulation: the weather scale
Abstract:
A long-lived blocking occurred over western Russia during summer of 2010. This blocking persisted especially during the whole July over the western Russia and caused various weather extremes in the Eurasian continent. In this study, we investigate the mechanism and predictability of Euro-Russian blocking in terms of the interaction between blocking and synoptic eddies or storm tracks, that is, the eddy feedback mechanism. The author adopt the selective absorption mechanism (SAM, Yamazaki and Itoh 2013) to explain the maintenance mechanism and predictability of Euro-Russian blocking during July. Using the ensemble data assimilation system (ALEDAS2) and AGCM (AFES) developed in APL, we conducted data analyses and ensemble weather (10-day) forecast experiments. Isentropic trajectory analyses in the reanalysis suggested that the SAM can work even in the summertime blocking event and in the forecast experiment the mechanism became more effective for ensemble members in which the blocking is successfully forecast. We also conducted a sensitivity experiments in which the Atlantic storm track were suppressed by a piecewise PV inversion method to evaluate the impact of the storm track on the maintenance of the blocking. The result indicates that the blocking can be substantially maintained by the feedback from the storm track. Those results suggested that the Atlantic storm track can substantially contribute to the maintenance and predictability of Euro-Russian blocking.

48th APL Open Forum

Date & Time:
30 November, Friday, 15:45-17:15
Place:
Meeting Room 1+2, 2nd floor, Conference Building, Yokohama Institute
Speaker1:
Masami Nonaka
Title:
Wind-driven and intrinsic interannual-to-decadal variability in the Kuroshio Extension
Abstract:
The Kuroshio Extension and its variability affect the atmosphere aloft through its large oceanic heat transport that is released to the atmosphere. It is therefore important to explore variability in the current to improve our understanding of air-sea interactions over the North Pacific region. While interannual-to-decadal variability in the Kuroshio Extension is primarily driven by atmospheric variability over the central/eastern North Pacific, the nonlinear jet has also intrinsic variability independent from the atmospheric forcing. To separate the wind-driven and intrinsic components of the Kuroshio Extension variability under realistic conditions, we analyze a ten-member ensemble, of fifty-year integration of an eddy-resolving OGCM driven by time-varying JRA55 reanalysis data. We consider the ensemble mean as the wind-driven, and the spread of ensemble members from their average as the intrinsic components. Filtering out effects of mesoscale eddies by the 13-month running mean, magnitudes of the wind-driven (4.7 cm/sec) and intrinsic (4.0 cm/sec) components are comparable. Meanwhile, the time series of the ensemble mean and spread show clearly different time scales: the former is dominated by decadal, and the latter by interannual variability. While possibly model dependent, thus result implies that the observed Kuroshio Extension may have a significant intrinsic component, which limit predictability of the jet on the interannual time scale.
Speaker2:
Ingo Richter
Title:
Examining the role of model bias in limiting tropical Atlantic prediction skill
Abstract:
Current seasonal prediction systems struggle to skillfully predict SST in the tropical Atlantic and are typically outperformed by statistical models. It is often assumed that this poor prediction skill is due to the severe SST biases and misrepresented variability patterns that most models feature in the region. The present study revisits this problem using linear inverse modeling (LIM) analysis. Using 35 fully coupled ocean-atmosphere GCMs from the pre-industrial control experiment (piControl) of the Coupled Model Intercomparison Project Phase 5 (CMIP5) we construct a LIM for each model based on tropical SSTs. These LIMs are then used to predict observed SSTs for the period 1948-2017. The results indicate that prediction skill in the tropical Atlantic is relatively insensitive to the biases of each model. Only some cases see a marked deterioration of prediction skill. Our analysis suggests that, in many CMIP5 models, misrepresentation of variability should not be a major stumbling block toward skillful prediction. This indicates that the current lack of prediction skill in the region is due to other factors, such as model initialization or inherent predictability limits due to noise.

47th APL Open Forum

Date & Time:
19 October, Friday, 15:45-17:15
Place:
Meeting Room 1+2, 2nd floor, Conference Building, Yokohama Institute
Speaker1:
Tsutomu Hihara
Title:
Validation of the JCOPE-T DA product using in situ data
Abstract:
We are constructing the JCOPE-T data assimilation and forecast system named as JCOPE-T DA. The operational calculation of JCOPE-T DA began at the end of July, more than two months data have already obtained. However we needed to improve the ocean model until early September. And also, JCOPE-T DA visualization website will be opened soon by JAXA. We will introduce detail.
Then, we will show the validation of JCOPE-T DA SST data using independent in situ SST data observed by Kuroshio Extension Observatory (KEO) buoy which is moored at 144.6˚E, 32.3˚N by PMEL/NOAA, Kuroshio-bokujyo buoys which are moored coastal area of Kochi, and SHINSEI MARU CTD data.
Speaker2:
Miho Ishizu
Title:
A marine carbon model coupled with an operational ocean model product for ocean acidification studies in the North Western Pacific
Abstract:
Ocean acidification causes serious damages to marine ecosystems such as coral reefs in the subtropical region and species or groups of organisms in the polar region. Damages due to increasing the ocean acidity are further predicted to affect broader areas and bring about great risks of marine organisms. We have developed a marine carbon model coupled with an operational ocean model product (JCOPE), aiming at investigating ongoing ocean acidification processes in the North Western Pacific, focusing on their associated physical-biogeochemical processes and social risks. The latest version of the model successfully reproduced reasonable values itself of chlorophyll-a, nutrients and pH, after improvements of initial conditions relating to carbon parameters and utilizations of multiple parameter optimization. Simulated seasonal variabilities, however, still have had a problem for nitrate and dissolved carbon etc in the subarctic region. Here we will show our model result with the observation data and what should be considered in our future model.

APL Seminar and Debriefing Session

Date & Time:
11 October, Thursday, 10:30-11:30
Place:
Room 403+404, 4th floor, IT Building, Yokohama Institute
Speaker:
Yuya Baba (Scientist, Application Laboratory)
Host:
Max-Planck Institute for Meteorology, Hamburg, Germany
Title:
Tropical variability in ICON-A with spectral cumulus parameterization
Abstract:
I visited the Max-Planck Institute for Meteorology (MPI-M) for one year as a visiting researcher since Sep. 2017. During my visit to MPI-M, I implemented my spectral cumulus parameterization (Baba 2018, Clim Dyn) in icosahedral non-hydrostatic atmospheric model (ICON-A) which is developed at MPI-M, and evaluated the results in terms of climatological error and intraseasonal variability. In my talk, I will show the superiority of my scheme compared to the original scheme of ICON-A. The details of the MPI-M and ICON model will also be introduced.

APL Guest Seminar

Date & Time:
10 October, Wednesday, 14:00-15:00
Place:
Room 1+2, 2nd floor, Conference Building, Yokohama Institute
Speaker:
Prof. P. N. Vinayachandran (Indian Institute of Science, Bangalore, India)
Title:
BoBBLE: Bay of Bengal Boundary Layer Experiment
Abstract:
The Bay of Bengal (BoB) plays a fundamental role in controlling the weather systems that make up the South Asian summer monsoon system. In particular, the southern BoB has cooler sea surface temperature (SST) that influence ocean–atmosphere interaction and impact on the monsoon. Compared to the southeast, the southwestern BoB is cooler, more saline, receives much less rain, and is influenced by the Summer Monsoon Current (SMC). To examine the impact of these features on the monsoon, the BoB Boundary Layer Experiment (BoBBLE) was jointly undertaken by India and the UK during June – July 2016. Physical and bio-geochemical observations were made using a CTD, five ocean gliders, a uCTD, a VMP, two ADCPs, Argo floats, drifting buoys, meteorological sensors and upper air radiosonde balloons. The observations were made along a zonal section at 8◦N between 85.3◦E and 89◦E with a 10-day time series at 89◦E, 8◦N. This paper presents the new observed features of the southern BoB from the BoBBLE field program, supported by satellite data. Key results from the BoBBLE field campaign show the Sri Lanka Dome and the SMC in different stages of their seasonal evolution and two freshening events during which salinity decreased in the upper layer leading to the formation of thick barrier layers. BoBBLE observations were taken during a suppressed phase of the intraseasonal oscillation; they captured in detail the warming of the ocean mixed layer and preconditioning of the atmosphere to convection.

APL Guest Seminar

Date & Time:
2 October, Tuesday, 10:30-12:00
Place:
Room 1+2, 2nd floor, Conference Building, Yokohama Institute
Speaker-1:
Prof. Rajib Maity (Indian Institute of Technology, Kharagpur, India)
Title-1:
Temporal evolution of hydroclimatic teleconnection and development of a time varying model for long-lead prediction of Indian summer monsoon rainfall
Abstract-1:
Several cases of failure in the prediction of Indian Summer Monsoon Rainfall (ISMR) are the major concern for long-lead prediction. In this talk, possible role of temporal evolution of association/linkage (inherent concept of temporal networks) with various factors and climatic indices across the globe will be discussed. Static models establish time-invariant (permanent) connections between such indices (predictors) and predictand (ISMR), whereas we hypothesize that such systems are temporally varying in nature. Considering hydroclimatic teleconnection with two major climate indices El Niño-Southern Oscillation (ENSO) and Equatorial Indian Ocean Oscillation (EQUINOO), we showed that the temporal persistence of the association is as low as three years. This talk will also cover an application of this concept through the development of a statistical time-varying model. Its prediction performance is compared against its static counterpart (time-invariant model). The proposed approach is able to capture the ISMR anomalies and successfully predicts the severe drought years too. Specifically, 64% more accurate performance (in terms of RMSE) is achievable by the recommended time-varying approach as compared to existing time-invariant concepts.

Further Reading:
Dutta, R., and Rajib Maity, (2018), Temporal evolution of hydroclimatic teleconnection and a time-varying model for long-lead prediction of Indian summer monsoon rainfall, Scientific Reports, 8:10778, Nature Publishing Group, DOI: 10.1038/s41598-018-28972-z.
Speaker-2:
Prof. Kironmala Chanda (Indian Institute of Technology, Dhanbad, India)
Title-2:
Characterization of Regional Precipitation Extremes and its Association with Global Climate Pattern
Abstract-2:
The development of a meteorological drought characterization index, named as Standardized Precipitation Anomaly Index (SPAI), will be discussed in the context of monsoon-dominated climatology. Compared with the widely used Standardized Precipitation Index (SPI), the SPAI will be demonstrated to be a more generalized index which is applicable for all kinds (both periodic and non-periodic) precipitation series for reflecting the consequences of meteorological droughts and wet spells. Next, the association of large scale oceanic-atmospheric circulation patterns with precipitation extremes, characterized in terms of SPAI, will be discussed. It is hypothesized that, rather than only a few, established teleconnection patterns, regional precipitation extremes are influenced by a concurrent effect of different climate variables from several regions across the globe. The hypothesis is tested by exploring the global anomaly fields of several climate variables such as sea surface temperature (SST), surface pressure (SP), air temperature (AT) and wind speed (WS) for their possible associations with regional scale precipitation extremes. Information from such global climate pattern (GCP) may be used to classify precipitation events into dry, wet and normal and it will be shown that a better classification may be achieved using the proposed GCP as against using only the traditionally used teleconnection patterns.

Further Reading:
Chanda K. and Maity, R., (2015), Uncovering Global Climate Fields Causing Local Precipitation Extremes, Hydrological Sciences Journal, Taylor and Francis, 61(10), 1227-1237, doi: 10.1080/02626667.2015.1006232.
Chanda K. and Maity, R. (2015), Meteorological Drought Quantification with Standardized Precipitation Anomaly Index (SPAI) for the Regions with Strongly Seasonal and Periodic Precipitation, Journal of Hydrologic Engineering, ASCE, 20(12), 06015007-1 – 06015007-8, DOI: 10.1061/(ASCE)HE.1943-5584.0001236.

44th APL Open Forum

Date & Time:
31 Augsust, Friday, 14:30-16:00
Place:
Meeting Room 1+2, 2nd floor, Conference Building, Yokohama Institute
Speaker 1:
Tak Ikeda
Title A:
Climate-based predictions of malaria outbreak in South Africa based on a machine learning framework
Abstract:
Globally, malaria cases have drastically dropped in recent years. However, high incidence and seasonal outbreaks of malaria continue to be a major issue in many regions of sub-Saharan Africa, such as Limpopo, South Africa. A machine learning framework involving a suite of learning algorithms incorporating malaria and climate data is used to predict the probability of outbreaks at district-level. Each algorithm is assessed, compared and ranked based on their performance for each district and season. Best performing models are used to predict the outbreak probability at three months lead time, in hopes to assist in the planning of intervention and link to decreasing the burden of disease by providing an early-warning system.
Title B:
Contour analysis of climatic factors in relation to diarrhoea for informed public health decision-making
Abstract:
Diarrhoeal disease is one of the leading causes of morbidity and mortality globally and is the second leading cause of death in children under 5 years of age. Factors related to diarrhoeal disease incidence include infection, malnutrition, and exposure to contaminated water and food. Climate factors also contribute to diarrhoeal disease where, in underdeveloped settings in particular, temperature and precipitation are associated with incidence of diarrhoeal disease in children. We aimed to explore the nature of the relationship between temperature, precipitation and diarrhoea case counts of hospital admissions among vulnerable communities living in a rural setting in north-eastern South Africa. We applied a novel approach of ‘contour analysis’ to visually examine simultaneous observations in frequencies of anomalously high and low diarrhoea case counts occurring in a particular season. Results were most striking in relation to precipitation among where we found that diarrhoea prevalence was unexpectedly higher during the dry season. Rural communities require adequate and uninterrupted water provision all-year round and healthcare providers should help to raise awareness about potential diarrhoeal risks especially during the dry season.
Speaker 2:
J. Venkata Ratnam
Title:
Seasonal forecasting of onset of summer rains over South Africa
Abstract:
We attempted to forecast the onset of summer rains over South Africa using seasonal forecasts generated by the Scale Interaction Experiment-Frontier Research Center for Global Change Version 2 (SINTEX-F2) seasonal forecasting system. Six-month lead forecasts of the 12-member SINTEX-F2 system, initialized on 1st August and covering the period 1998 to 2015 were used for the study. The SINTEX-F2 forecast was also downscaled using dynamical and statistical techniques to improve the precipitation forecasts. The Weather Research and Forecasting (WRF) model with two cumulus parameterization schemes was used to dynamically downscale the SINTEX-F2 forecasts. The WRF and SINTEX-F2 precipitation forecasts were corrected for biases using linear scaling method with 31-day moving window. The results indicate the onset dates derived from the raw and bias corrected model precipitation forecasts to have realistic spatial distribution over South Africa. However, the onset dates are predictable with less errors only over north-eastern parts of the country.

APL Guest Seminar

Date & Time:
7 August, Tuesday, 14:30-15:30
Place:
Room 403+404, 4th Floor, IT Building
Speaker:
Prof. Elena Surovyatkina (Potsdam Institute for Climate Impact Research, Germany)
Title:
Monsoon forecast under climate change
Abstract:
Seasonal variability implies two aspects: first, the seasons do not begin at fixed dates but must be determined by observation and are known only after the fact; and second, a new season begins at different dates in different parts of the country and over the world. Seasonal variability strongly affects different aspects of human life such as agricultural productivity and food security, economic growth and political stability. In Central India, the variability of Monsoon is quite high due to local changes such as rapid urbanization, industrialization. The forecasting of climate phenomena on a seasonal scale is a challenge mostly because of there is no recent historical precedent for such changing in the climate system.
In our study of the Indian monsoon season, we have found the evidence in observational data that we can consider the onset of monsoon as a critical transition – a sudden transition to the monsoon when critical thresholds (in particular, in near-surface air temperature, relative humidity) are reached. This finding allows us using the critical transition theory for developing the Tipping elements approach for prediction of onset and withdrawal dates of the summer monsoon under the conditions of climate change.
Our prediction relies on observations of near-surface air temperature and relative humidity from both the ERA-40 and NCEP/NCAR reanalyses. Our results show that our method allows predicting the monsoon not only retrospectively (over the period 1951-2015) but also in the future. In 2016 and 2017 we successfully predicted the onset and withdrawal dates of the Southwest monsoon over the central part of India for 40 and 70 days in advance respectively. Hence, we proved that such early prediction of season timing is possible.
The proposed approach is applicable for different kind of season, which exhibits properties of critical transition. Our prediction is based on observational data only when the model cannot accurately anticipate the transition or does not exist yet.

References:
[1] Stolbova, V., E. Surovyatkina, B. Bookhagen, and J. Kurths (2016): Tipping elements of the Indian monsoon: Prediction of onset and withdrawal. GRL 43, 1–9 [doi:10.1002/2016GL068392]
[2] https://www.pik-potsdam.de/services/infodesk/forecasting-indian-monsoon

44th APL Open Forum

Date & Time:
27 July, Friday, 15:45-17:15
Place:
Meeting Room 1+2, 2nd floor, Conference Building, Yokohama Institute
Speaker 1:
Takeshi Doi
Title:
Effects of the WWB/EWS parameterization on ENSO prediction by the SINTEX-F system
Abstract:
Intra-seasonal surface westerly wind bursts (WWB)/easterly wind surges (EWS) in the tropical Pacific plays important roles in the onset of El Nino/La Nina. However, the latest version of the SINTEX-F seasonal prediction system tends to underestimate the chance of occurrence of those winds. This problem may cause the low prediction skill of the onest of ENSO and the over-confident problems.
In this study, we developed the WWB/EWS-like stochastic forcing parameterization, and examined the effects on ENSO prediction by the SINTEX-F system. In my talk, failure of 2014 El Nino prediction will be the focus although the results are still preliminary.
Speaker 2:
Ayako Yamamoto
Title:
Multidecadal atmosphere-ocean feedback loop over the North Atlantic in MIROC6 model
Abstract:
A synthesis of previous studies seems to point towards the possible existence of a multidecadal atmosphere-ocean feedback loop over the North Atlantic, such that the atmospheric variability associated with the positive phase of North Atlantic Oscillation precedes an increase in Atlantic meridional overturning circulation, leading to a North Atlantic basin-wide warming of the sea surface temperature. Observations further suggests that this warming of the North Atlantic basin leads the negative phase of North Atlantic Oscillation, thereby proceeding to the opposite sign of the loop. Despite the importance of such multidecadal feedback loop not only for forecasting these low-frequency phenomena but also for isolating the internal variability from the external forcing, previous studies have indicated that a majority of CMIP5 models fail to reproduce such feedback loop, due possibly to the underrepresentation of low-clouds and/or the stratosphere-troposphere coupling.
In this study, we investigate such multidecadal relationship using a preindustrial control simulation of a coupled climate model, MIROC6 model, which now includes a better representation of both low-clouds and the stratosphere-troposphere couplings. Our results indicate that MIROC6 has a potential to be able to simulate such relationship, which is suppressed in the previous version of the same model, MIROC5. We have found that the possible cause of this difference between the two models is likely due to the better representation of the low-clouds as well as the associated feedback, which is an important process which determines the tropical arm of the sea surface temperature.

43rd APL Open Forum

Date & Time:
29 June, Friday, 15:45-17:15
Place:
Meeting Room 1+2, 2nd floor, Conference Building, Yokohama Institute
Speaker 1:
Kunihiro Aoki
Title:
Principle
Abstract:
Science is a world created for describing the nature. This world originates from only a few of principles. Recasting the principles could lead to opening a new world that describes the nature more precisely, like Einstein’s theory of relativity. This talk shows a new formulation of the Reynolds stress that changes the state of the oceanic jet such as the Kuroshio Extension, Gulf Stream, or Antarctic Circumpolar Current. Different from the normal definition of the Reynolds stress, which is derived from the velocity associated with oceanic eddy, this formula is based on the principle that the velocity is determined by the shape of the eddy. In this talk, we will show the findings brought from this recasting. Also, this formula is applied to the real ocean with the help of a machine learning method. This talk reveals the theoretical structure of the general machine learning method, along with the underlying principles, and discusses the prospect of AI, which is a branch of the machine learning method.
Speaker 2:
Nobumasa Komori
Title:
Experimental seasonal climate prediction using CFES
Abstract:
An experimental seasonal climate prediction system has been developed based on the Coupled atmosphere-ocean general circulation model for the Earth Simulator (CFES). Following the well-established system based on the SINTEX-F model, initial conditions for seasonal climate prediction are constructed by strongly nudging sea surface temperature (SST) to observed one.
The atmospheric component of CFES has the resolution of T119 in the horizontal and 48 sigma-layers in the vertical with the top level placed at about 3 hPa. The oceanic component has a resolution of 1/2 degree in the directions of both longitude and latitude and 54 levels in the vertical. They are coupled every hour.
12-member ensemble 6-month predictions from the 1st day of March, June, September, and December have been conducted from 1983 through 2017, after 32-years of coupled spin-up integration with SST-nudging to the observed climatology. The experimental system exhibits skill in predicting SST variability in the tropical Pacific.
Prediction skill of sea-ice concentration in the Arctic and Antarctic Oceans, and the seasonal prediction from 1 June 2018 will also be presented.

42th APL Open Forum

Date & Time:
1 June, Friday, 15:45-17:15
Place:
Meeting Room 403+404, 4th floor, IT Building, Yokohama Institute
Agenda:
a) Monitoring and prediction (5 min each)
  1. Kuroshio/Oyashio Monitoring (Toru Miyama)
  2. Climate Briefing (Yushi Morioka)
b) Two talks (20-25 min each)
  1. Yushi Morioka, “Decadal climate predictability in the South Atlantic and southern Indian Oceans revealed using the SINTEX-F2 model”
  2. Tomomichi Ogata, “Mid-latitude source of the ENSO-spread in SINTEX-F ensemble predictions”
a) Speaker:
Yushi Morioka
Title:
Decadal climate predictability in the South Atlantic and southern Indian Oceans revealed using the SINTEX-F2 model
Abstract:
Decadal climate predictability in the South Atlantic and southern Indian Oceans is explored using the SINTEX-F2 CGCM with two initialization schemes: one is to initialize the model SST using a simple SST-nudging scheme, and another is to additionally initialize the subsurface ocean temperature and salinity using 3DVAR data assimilation scheme. Decadal reforecast experiments with the SST initialization only show moderately high skills in predicting the observed decadal variability over the Southwest Indian Ocean, but not over the South Atlantic. Further experiments with the 3DVAR subsurface ocean initialization show much improvement in the prediction skills of decadal SST variability over the Southeast Atlantic. These results suggest that the SST-initialization may be useful for decadal SST prediction in the region where the relatively strong air-sea coupling takes place due to existence of midlatitude SST front, while the subsurface ocean initialization is indispensable for skillful predictions of decadal SST variability in the region where the air-sea coupling is weakly involved.
b) Speaker:
Tomomichi Ogata
Title:
Mid-latitude source of the ENSO-spread in SINTEX-F ensemble predictions
Abstract:
The ensemble spread of seasonal prediction is investigated in this study to understand its role in the predictability of El Niño/Southern Oscillation (ENSO) based on the results of SINTEX-F2, a coupled ocean-atmosphere general circulation model. In the SINTEX-F2 seasonal prediction system, the first ENSO precursor appears as a cyclonic wind anomaly over the central north Pacific in boreal winter (January).This is followed by warm SST, positive rainfall and cross-equatorial southerly wind anomalies in the northern hemisphere during spring (particularly in April). These anomalies in April are accompanied by westerly wind anomaly in the western equatorial Pacific. Finally, El Niño-like conditions with warm SST and positive rainfall anomalies become dominant in the ensemble standard deviation after boreal summer.

APL Guest Seminar

Date & Time:
28 May, Monday, 14:30-15:30
Place:
Meeting Room 1+2, 2nd floor, Conference Building, Yokohama Institute
Speaker:
Ms. Tina Dippe (GEOMAR Helmholtz Centre for Ocean Research, Germany)
Title:
How dynamical is the Atlantic Niño?
Abstract:
Interannual variability of equatorial Atlantic sea surface temperatures (SST) is of socio-economic importance for the adjacent continents. The dominant mode of interannual SST variability is the Atlantic Niño, which is named in reference to the Pacific El Niño. It is strongest in May-July and peaks again in November-December, affecting precipitation patterns throughout the Atlantic tropics. In my talk, I will address two issues regarding the Atlantic Niño. First, I will assess how strongly ocean dynamics contribute to the observed Atlantic Niño variability. Because current coupled climate models are heavily biased in the tropical Atlantic, I will use simulations of the Kiel Climate Model to evaluate how the SST warm bias affects the ability of the model to reproduce dynamical contributions to Atlantic Niño variability. Second, I take a closer look at the observed Atlantic Bjerknes feedback — an important driver of dynamical Atlantic Niño variability — and assess how symmetric the feedback is for both warm and cold Atlantic Niño events, and summer and winter events.

APL Guest Seminar

Date & Time:
3 April, Tuesday, 14:00-15:00
Place:
Meeting Room 1+2, 2nd floor, Conference Building, Yokohama Institute
Speaker:
Dr. Max Yaremchuk (U.S. Naval Research Laboratory)
Title:
Adjoint-free 4D variational data assimilation into regional models
Abstract:
The ongoing trend toward parallelization in computer technologies propels ensemble methods to the forefront of data assimilation studies in geophysics. Of particular interest are ensemble techniques which do not require the development of tangent linear numerical models and their adjoints for optimization. Another important advantage of these techniques is a relatively low cost of implementation with a numerical model treated by the approach as a black box. In this talk, an adjoint-free 4dVar methodology is described and demonstrated in an application estimating initial conditions of two numerical models: the Navy Coastal Ocean Model (NCOM) and the surface wave model (WAM). It is shown that a4dVar is capable of providing forecast skill similar to that of conventional 4dVar at comparable computational expense while being less susceptible to excitation of ageostrophic modes that are not supported by observations. Prospects of further development of the a4dVar methods and position of the presented technique in a swarm of the ensemble-based 4dVar methods are discussed.

40th APL Open Forum

Date & Time:
23 March, Friday, 15:45-17:15
Place:
Meeting Room 1+2, 2nd floor, Conference Building, Yokohama Institute
Speaker 1:
Toru Miyama
Title:
Recent warming of the Oyashio region
Abstract:
The sea surface temperature of the Oyashio region in summer has abruptly increased from 2010. Observations and an ocean reanalysis show that the warming occurred not only at the surface but also at greater depths. Downward air-sea heat flux is likely to be a minor factor because the increase of the heat flux did not collocate with the SST increase and cannot explain subsurface warming. Salinity in summer also increased in parallel with the temperature in the Oyashio region. The rises in the temperature and salinity suggest the weakening of the Oyashio influence and the strengthening of the Kuroshio influence. The sea surface height and the velocity show that the first intrusion of the Oyashio in summer weakened from 2010 because of the stronger anticyclonic eddy. The rise of the water temperature may have affected a catch of yellowtail.
Speaker 2:
Sergey Varlamov
Title:
Recent developments in JCOPE coastal ocean modeling
Abstract:
During the last year+ the JCOPE real-time coastal modeling system underwent many modifications and was used for many practical and research applications. Main directions of system improvement included:
- transition of code to MPI parallel version
- support of operations of 2 levels of nesting with highest spatial resolution of models up to ~200 meters
- improvement of river discharge module and application of model for analysis of extremal run-off from Japanese rivers (paper in Journal of Hydrology, 2017)
- introduction of multiple scales 3DVar assimilation to the ocean model
- etc.
Real-time modeling results were requested for many cases that included:
- informational support for JAMSTEC Chikyu operations
- local information systems installations for areas of Ogasawara, Chiba, Sukumo
As an example, the details of realization and analysis of impact from river discharges to the coastal environment will be provided.

APL Guest Seminar

Date & Time:
20 March, Tuesday, 14:00-15:00
Place:
Meeting Room 1+2, 2nd floor, Conference Building, Yokohama Institute
Speaker:
Prof. Rajib Maity (Indian Institute of Technology Kharagpur)
Title:
Hydroclimatic Modelling for Teleconnection, Downscaling, Probabilistic Prediction using Statistical and AI based Techniques
Abstract:
In the recent scenario of climate changes, the natural variability and uncertainty associated with the hydrologic variables is of great concern to the community. Hydroclimatic teleconnection between hydrologic variables and large-scale atmospheric circulation phenomena is being studied worldwide and gaining more and more interest in recent years due to its potential use for analyzing variability and uncertainty of hydrologic variables. This talk will provide an overview of research activity in the research group of Dr. Rajib Maity, IIT Kharagpur related to hydroclimatic modelling for teleconnection, downscaling and probabilistic prediction of different hydrologic variables both at large-scale and basin-scale. Illustration will include Indian summer monsoon rainfall, basin-scale streamflow, soil moisture, precipitation downscaling, drought characterization and prediction etc. To model the complex non-linear relationship different time-varying and time-invariant statistical and AI based Techniques will be discussed.

APL Guest Seminar

Date & Time:
8 March, Thursday, 14:00-15:00
Place:
Meeting Room 1+2, 2nd floor, Conference Building, Yokohama Institute
Speaker:
Prof. Golan Bel (Ben Gurion University of the Negev, Israel)
Title:
Decadal Climate Predictions Using Sequential Learning Algorithms
Abstract:
Ensembles of climate models are commonly used to improve climate predictions and assess the uncertainties associated with them. Weighting the models according to their performances holds the promise of further improving their predictions. Decadal climate predictions, which are initialized with observed conditions, are characterized by two main sources of uncertainties—internal and model variabilities. Using an ensemble of climate model simulations from the CMIP5 decadal experiments, we quantified the total uncertainty associated with these predictions and the relative importance of each source. The model uncertainties that contribute greatly to the total uncertainties in most regions, for all the variables considered here, may be reduced by weighting the models in the ensemble.
Sequential learning algorithms (SLAs) are used to reduce the forecast errors and reduce the uncertainties. Three different SLAs are considered, and their performances are compared with those of an equally weighted ensemble, a linear regression, and the climatology. Predictions of four different variables—the surface temperature, the zonal and meridional wind, and the pressure—are considered. The spatial distributions of the performances are presented, and the statistical significance of the improvements achieved by the SLAs is tested. The reliability of the SLAs is also tested, and the advantages and limitations of the different performance measures are discussed. It was found that the best performances of the SLAs are achieved when the learning period is comparable to the prediction period. The spatial distribution of the SLAs performance showed that they are skillful and better than the other forecasting methods over large continuous regions. This finding suggests that, despite the fact that each of the ensemble models is not skillful, the models were able to capture some physical processes that resulted in deviations from the climatology and that the SLAs enabled the extraction of this additional information.

APL Guest Seminar

Date & Time:
20 February, Tuesday, 10:30-11:30
Place:
Meeting Room, 4th floor, IT Building, Yokohama Institute
Speaker:
Dr. H. Annamalai (International Pacific Research Center, UH Manoa, Hawaii, US)
Title:
Grand Challenges in Monsoon Modeling: Representation of Processes and Source of Model Errors

39th APL Open Forum

Date & Time:
26 January, Friday, 15:45-17:15
Place:
Meeting Room 1+2, 2nd floor, Conference Building, Yokohama Institute
Speaker 1:
Hideharu Sasaki
Title:
Acceleration of Indonesian Throughflow by tidal mixing scheme in OFES2
Abstract:
The impact of tidal mixing on mass transport of the Indonesian Through Flow (ITF) is investigated by comparison of the high-resolution quasi-global ocean simulations with and without the tidal mixing scheme. The ITF in the simulation with the scheme is accelerated by the increase of pressure difference between the Pacific and Indian Ocean, corresponding to the large sea surface height (SSH) difference. The SSH to the south of Mindanao Island becomes high locally, which also geophysically accelerates the ITF entering the Celebes Sea. The SSH increase is possibly induced by Rossby waves with large negative density decrease within and below the lower thermocline, which is generated by tidal mixing over shallow rough topography in the area of island chains. These results indicate that the impacts of tidal mixing on the vertical water characteristics within and below the thermocline, large in the Pacific, cause the ITF acceleration.
Speaker 2:
Pascal Oettli
Title:
Experimental Statistical Modelling of Oil Palm Fresh Fruit Bunches Monthly Yields in Malaysia: Preliminary Results
Abstract:
Previously, a linear model has been constructed, taking into account the effects of local conditions and remote climate modes on the interannual variability of oil palm fresh fruit bunches (FFB) total yields in Malaysia. This model has shown some skills in predicting the total FFB yield, but, by nature, has also some limitations. In order to improve the statistical prediction of annual production, the seasonal variability of FFB is explored, as a preliminary step to statistical seasonal simulation and prediction of monthly FFB production.

APL Guest Seminar

Date & Time:
15 January, Monday, 11:00-12:00
Place:
Meeting Room 1+2, 2nd floor, Conference Building, Yokohama Institute
Speaker:
Prof. Katsumi Tsukamoto (Nihon University and Tokyo University [emeritus])
Title:
Oceanic migration and spawning ecology of freshwater eels in the western North Pacific
Abstract:
Katsumi Tsukamoto has contributed to the field of fish migration through his 40-years career of wide-ranging research on diadromous fishes (ayu, salmon, eels) that migrate between the sea and freshwater. He led his research team to collect freshwater eel eggs in the ocean for the first time in the world and discovered the spawning area of the Japanese eel in the western Pacific, which was highly publicized in Japan. Even after some of the spawning areas of freshwater eels were outlined about 100 years ago in the Atlantic, their spawning migration and natural reproductive ecology remained a mystery in the mist of ocean. Recent progress in marine biology, technologies and oceanographic methodologies lead us to successful collection of the Japanese eel eggs, hatched larvae and spawning condition adults in the estimated spawning area of the western North Pacific, and finally revealed a long-lasting eel problem since the ancient Greek Aristotle more than 2000 years ago. The collection validates the hypotheses of new moon spawning at seamount area in the southern West Marina Ridge and confirms that salinity fronts and the seamount chain are important determinants of their spawning location. This type of spawning may help forming of spawning aggregation of males and females and reduce predation to facilitate reproductive success. The depths where adults and newly-hatched larvae were captured indicate eel spawning occurs in shallower layers of about 200 m and not at great depths. Ovaries of female Japanese eel and giant mottled eel adults were polycyclic, suggesting freshwater eels can spawn more than once during a spawning season. Monthly and annual changes of spawning location based on a decadal collection data of eggs, preleptocephali (hatched eel larvae) and adult eels suggested a recent southern shift of the spawning locations of the species that could be a major factor causing a drastic decline of the glass eel recruitment into East Asia through ocean atmospheric change in the western North Pacific. Recent progress of research on oceanic migration of adult eels by satellite-relayed pop up tag will also be presented.