The observation operator (OO) is essential in data assimilation (DA) to derive the model equivalent of observations from the model variables. In the satellite DA, the OO for satellite microwave brightness temperature (BT) is usually based on the radiative transfer model (RTM) with a bias correction procedure. To explore the possibility to obtain OO without using physically based RTM, this study applied machine learning (ML) as OO (MLOO) to assimilate BT from Advanced Microwave Sounding Unit-A (AMSU-A) channels 6 and 7 over oceans and channel 8 over both land and oceans under clear-sky conditions. We used a reference system, consisting of the nonhydrostatic icosahedral atmospheric model (NICAM) and the local ensemble transform Kalman filter (LETKF). The radiative transfer for TOVS (RTTOV) was implemented in the system as OO, combined with a separate bias correction procedure (RTTOV-OO). The DA experiment was performed for 1 month to assimilate conventional observations and BT using the reference system. Model forecasts from the experiment were paired with observations for training the ML models to obtain ML-OO. In addition, three DA experiments were conducted, which revealed that DA of the conventional observations and BT using ML-OO was slightly inferior, compared to that of RTTOV-OO, but it was better than the assimilation based on only conventional observations. Moreover, ML-OO treated bias internally, thereby simplifying the overall system framework. The proposed ML-OO has limitations due to (1) the inability to treat bias realistically when a significant change is present in the satellite characteristics, (2) inapplicability for many channels, (3) deteriorated performance, compared with that of RTTOV-OO with respect to accuracy and computational speed, and (4) physically based RTM is still used to train the ML-OO. Future studies can alleviate these drawbacks, thereby improving the proposed ML-OO.
在数据同化(DA)中，观测算子从模型变量中导出观测值的模型等价是必不可少的。在卫星数据分析中，卫星微波亮度温度(BT)的OO通常是基于辐射传输模型(RTM)并进行偏置校正。为了探索在不使用基于物理的RTM的情况下获得OO的可能性，本研究应用机器学习(ML)作为OO (MLOO)来吸收来自先进微波探测单元- a (AMSU-A)在海洋上的6和7频道以及晴天条件下陆地和海洋上的8频道的BT。我们使用了一个由非流体静力二十面体大气模型(NICAM)和局部系综变换卡尔曼滤波(LETKF)组成的参考系统。TOVS的辐射传递(RTTOV)在系统中作为OO实现，并结合单独的偏置校正程序(RTTOV-OO)。采用参考系统进行了为期1个月的DA实验，以同化常规观测和BT。从实验中得到的模型预测与观测结果配对，用于训练ML模型以获得ML- oo。此外，进行了3次数据同化实验，结果表明，与RTTOV-OO同化相比，使用ML-OO同化常规观测值和BT的数据同化效果略差，但优于仅使用常规观测值同化。此外，ML-OO在内部处理了偏差，从而简化了整个系统框架。所提出的ML-OO存在以下局限性:(1)当卫星特性发生重大变化时，无法真实地处理偏差;(2)不适用于许多信道;(3)与RTTOV-OO相比，性能在精度和计算速度方面有所下降;(4)仍然使用基于物理的RTM来训练ML-OO。未来的研究可以减轻这些缺点，从而改进所提出的ML-OO。
{"title":"A Machine Learning Approach to the Observation Operator for Satellite Radiance Data Assimilation","authors":"Jianyu LIANG, Koji TERASAKI, Takemasa MIYOSHI","doi":"10.2151/jmsj.2023-005","DOIUrl":"https://doi.org/10.2151/jmsj.2023-005","url":null,"abstract":"The observation operator (OO) is essential in data assimilation (DA) to derive the model equivalent of observations from the model variables. In the satellite DA, the OO for satellite microwave brightness temperature (BT) is usually based on the radiative transfer model (RTM) with a bias correction procedure. To explore the possibility to obtain OO without using physically based RTM, this study applied machine learning (ML) as OO (MLOO) to assimilate BT from Advanced Microwave Sounding Unit-A (AMSU-A) channels 6 and 7 over oceans and channel 8 over both land and oceans under clear-sky conditions. We used a reference system, consisting of the nonhydrostatic icosahedral atmospheric model (NICAM) and the local ensemble transform Kalman filter (LETKF). The radiative transfer for TOVS (RTTOV) was implemented in the system as OO, combined with a separate bias correction procedure (RTTOV-OO). The DA experiment was performed for 1 month to assimilate conventional observations and BT using the reference system. Model forecasts from the experiment were paired with observations for training the ML models to obtain ML-OO. In addition, three DA experiments were conducted, which revealed that DA of the conventional observations and BT using ML-OO was slightly inferior, compared to that of RTTOV-OO, but it was better than the assimilation based on only conventional observations. Moreover, ML-OO treated bias internally, thereby simplifying the overall system framework. The proposed ML-OO has limitations due to (1) the inability to treat bias realistically when a significant change is present in the satellite characteristics, (2) inapplicability for many channels, (3) deteriorated performance, compared with that of RTTOV-OO with respect to accuracy and computational speed, and (4) physically based RTM is still used to train the ML-OO. Future studies can alleviate these drawbacks, thereby improving the proposed ML-OO.","PeriodicalId":17476,"journal":{"name":"Journal of the Meteorological Society of Japan","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136367735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Retrograde long waves in the higher latitudes of the Northern Hemisphere can episodically attain large amplitudes and sustain coherent phase propagation for 2 – 3 weeks. The potential influence of such waves on extended-range weather forecast has been conjectured but not systematically quantified. Using a set of ensemble reforecast data, this study examined the predictability associated with an extraordinary retrograde-wave episode in the 1979 – 80 winter. Quantified by the anomaly correlation of the 500 hPa geopotential height in the 40 – 70°N latitudi nal band, increased week-2 predictability was found within the subperiod with the presence of coherent retrograde waves. Some individual forecasts made within the retrograde-wave event exhibited the behavior of “return of skills”. The results suggest a future investigation into the relation between the elevated level of anomaly correlation in week-2 and detailed dynamics of the retrograde waves.
{"title":"Predictability Associated with High-Latitude Retrograde Waves in the 1979-80 Winter Season","authors":"Huang Huei-Ping, Raghunathan Girish Nigamanth","doi":"10.2151/JMSJ.2022-012","DOIUrl":"https://doi.org/10.2151/JMSJ.2022-012","url":null,"abstract":"Retrograde long waves in the higher latitudes of the Northern Hemisphere can episodically attain large amplitudes and sustain coherent phase propagation for 2 – 3 weeks. The potential influence of such waves on extended-range weather forecast has been conjectured but not systematically quantified. Using a set of ensemble reforecast data, this study examined the predictability associated with an extraordinary retrograde-wave episode in the 1979 – 80 winter. Quantified by the anomaly correlation of the 500 hPa geopotential height in the 40 – 70°N latitudi nal band, increased week-2 predictability was found within the subperiod with the presence of coherent retrograde waves. Some individual forecasts made within the retrograde-wave event exhibited the behavior of “return of skills”. The results suggest a future investigation into the relation between the elevated level of anomaly correlation in week-2 and detailed dynamics of the retrograde waves.","PeriodicalId":17476,"journal":{"name":"Journal of the Meteorological Society of Japan","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68296285","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Different Future Changes between Early and Late Summer Monsoon Precipitation in East Asia","authors":"H. Endo, A. Kitoh, R. Mizuta, T. Ose","doi":"10.2151/JMSJ.2021-073","DOIUrl":"https://doi.org/10.2151/JMSJ.2021-073","url":null,"abstract":"","PeriodicalId":17476,"journal":{"name":"Journal of the Meteorological Society of Japan","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42011282","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Application of a Nudged General Circulation Model to the Interpretation of the Mean Age of Air Derived from Stratospheric Samples in the Tropics","authors":"T. H. Nguyen, K. Ishijima, S. Sugawara, F. Hasebe","doi":"10.2151/JMSJ.2021-056","DOIUrl":"https://doi.org/10.2151/JMSJ.2021-056","url":null,"abstract":"","PeriodicalId":17476,"journal":{"name":"Journal of the Meteorological Society of Japan","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2021-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47633819","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Marylis Barreyat, P. Chambon, J. Mahfouf, G. Faure, Yasutaka Ikuta
{"title":"A 1D Bayesian Inversion Applied to GPM Microwave Imager Observations: Sensitivity Studies","authors":"Marylis Barreyat, P. Chambon, J. Mahfouf, G. Faure, Yasutaka Ikuta","doi":"10.2151/JMSJ.2021-050","DOIUrl":"https://doi.org/10.2151/JMSJ.2021-050","url":null,"abstract":"","PeriodicalId":17476,"journal":{"name":"Journal of the Meteorological Society of Japan","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2021-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43922808","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yinglu Wu, Yu‐Chieng Liou, Yi-Chuan Lo, S. Tai, Shao-Fan Chang, Juanzhen Sun
{"title":"Precipitation Processes of a Thunderstorm Occurred on 19 August 2014 in Northern Taiwan Documented by Using a High Resolution 4DVar Data Assimilation System","authors":"Yinglu Wu, Yu‐Chieng Liou, Yi-Chuan Lo, S. Tai, Shao-Fan Chang, Juanzhen Sun","doi":"10.2151/JMSJ.2021-049","DOIUrl":"https://doi.org/10.2151/JMSJ.2021-049","url":null,"abstract":"","PeriodicalId":17476,"journal":{"name":"Journal of the Meteorological Society of Japan","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2021-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46489927","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Statistical Intercomparison of Similarity Metrics in Sea Level Pressure Pattern Classification","authors":"Takuto Sato, H. Kusaka","doi":"10.2151/JMSJ.2021-047","DOIUrl":"https://doi.org/10.2151/JMSJ.2021-047","url":null,"abstract":"","PeriodicalId":17476,"journal":{"name":"Journal of the Meteorological Society of Japan","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2021-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45749996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Shibuya, M. Nakano, C. Kodama, T. Nasuno, K. Kikuchi, M. Satoh, H. Miura, T. Miyakawa
{"title":"Prediction Skill of the Boreal Summer Intra-Seasonal Oscillation in Global Non-hydrostatic Atmospheric Model Simulations with Explicit Cloud Microphysics","authors":"R. Shibuya, M. Nakano, C. Kodama, T. Nasuno, K. Kikuchi, M. Satoh, H. Miura, T. Miyakawa","doi":"10.2151/JMSJ.2021-046","DOIUrl":"https://doi.org/10.2151/JMSJ.2021-046","url":null,"abstract":"","PeriodicalId":17476,"journal":{"name":"Journal of the Meteorological Society of Japan","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2021-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44191107","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The boreal summer intraseasonal oscillation (BSISO) is among the most pronounced subseasonal variability in the tropics during boreal summer. Compared with its wintertime counterpart, the so-called Madden–Julian oscillation (MJO), the BSISO convection displays more complicated spatiotemporal evolution, characterized by northward propagation over the northern Indian Ocean and western North Pacific as well as eastward propagation along the equator. It exerts a strong effect on a broad range of tropical weather and climate phenomena, such as tropical cyclogenesis, monsoon onset, and active/break cycles, among others. Our fundamental understanding of the BSISO has steadily advanced: so far various aspects of the BSISO have been described, and several theories that aim to elucidate its northward propagation have been proposed. Yet, our skill to simulate the BSISO by gen - eral circulation models remains unsatisfactory, though it has been improved. This paper reviews some fundamen - tal aspects of the BSISO from the viewpoint of observation, theory, and modeling.
{"title":"The Boreal Summer Intraseasonal Oscillation (BSISO): A Review","authors":"K. Kikuchi","doi":"10.2151/JMSJ.2021-045","DOIUrl":"https://doi.org/10.2151/JMSJ.2021-045","url":null,"abstract":"The boreal summer intraseasonal oscillation (BSISO) is among the most pronounced subseasonal variability in the tropics during boreal summer. Compared with its wintertime counterpart, the so-called Madden–Julian oscillation (MJO), the BSISO convection displays more complicated spatiotemporal evolution, characterized by northward propagation over the northern Indian Ocean and western North Pacific as well as eastward propagation along the equator. It exerts a strong effect on a broad range of tropical weather and climate phenomena, such as tropical cyclogenesis, monsoon onset, and active/break cycles, among others. Our fundamental understanding of the BSISO has steadily advanced: so far various aspects of the BSISO have been described, and several theories that aim to elucidate its northward propagation have been proposed. Yet, our skill to simulate the BSISO by gen - eral circulation models remains unsatisfactory, though it has been improved. This paper reviews some fundamen - tal aspects of the BSISO from the viewpoint of observation, theory, and modeling.","PeriodicalId":17476,"journal":{"name":"Journal of the Meteorological Society of Japan","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2021-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47351028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hidetaka Hirata, R. Kawamura, M. Nonaka, K. Tsuboki
{"title":"Kuroshio-Enhanced Convective Rainband Associated with an Extratropical Cyclone in the Cold Season","authors":"Hidetaka Hirata, R. Kawamura, M. Nonaka, K. Tsuboki","doi":"10.2151/JMSJ.2021-043","DOIUrl":"https://doi.org/10.2151/JMSJ.2021-043","url":null,"abstract":"","PeriodicalId":17476,"journal":{"name":"Journal of the Meteorological Society of Japan","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2021-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47736409","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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