EFSO at different geographical locations verified with observing-system experiments

ひとつひとつの観測データが気象予測に与える影響を簡易に評価する手法を確認 --北極の観測データは7日先の北米気象予測の改善に貢献することも明らかに--. 京都大学プレスリリース. 2021-04-30.An ensemble-based forecast sensitivity to observations (EFSO) diagnosis has been implemented in an atmospheric general circulation model–ensemble Kalman filter data assimilation system to estimate the impacts of specific observations from the quasi-operational global observing system on weekly short-range forecasts. It was examined whether EFSO reasonably approximates the impacts of a subset of observations from specific geographical locations for 6-hour forecasts, and how long the 6-hour observation impacts can be retained during the 7-day forecast period. The reference for these forecasts was obtained from 12 data denial experiments in each of which a subset of three radiosonde observations launched from a geographical location was excluded. The 12 locations were selected from three latitudinal bands comprising (i) four Arctic regions, (ii) four midlatitude regions in the Northern Hemisphere, and (iii) four tropical regions during the Northern Hemisphere winter of 2015/16. The estimated winter-averaged EFSO-derived observation impacts well corresponded to the 6-hour observation impacts obtained by the data denials and EFSO could reasonably estimate the observation impacts by the data denials on short-range (6-hour to 2-day) forecasts. Furthermore, during the medium-range (4-day to 7-day) forecasts, it was found that the Arctic observations tend to seed the broadest impacts and their short-range observation impacts could be projected to beneficial impacts in Arctic and midlatitude North American areas. The midlatitude area located just downstream of dynamical propagation from the Arctic toward the midlatitudes. Results obtained by repeated Arctic data-denial experiments were found to be generally common to those from the non-repeated experiments

The effective use of shortwave penetration below the ocean surface in a MOM3-based ocean general circulation model

There are two problems with the shortwave penetration scheme used in Modular Ocean Model version 3 (MOM3): (i) the spatiotemporal variability of the thickness of the first layer resulting from the free surface is not considered, and (ii) shortwave irradiance penetrates the ocean bottom. Because both of these problems can cause artificial heat sources or sinks, their effects are evaluated in the present study using a MOM3-based ocean general circulation model. The first problem creates an artificial heat sink (source) in the regions of positive (negative) sea surface height (SSH) with a maximum amplitude greater than 10 W m-2 and decreases (increases) sea surface temperature (SST) by up to 0.3°C on the basis of annual mean. This change in SST leads to a reduction in global mean evaporation and, as a result, an increase in SSH, which enhances the artificial heat sink. After several years of integration, this positive feedback amplifies the effects of the first problem in cases of stand-alone ocean simulations forced by freshwater flux. The estimated artificial heat sink induced by the second problem reaches 50 W m-2, and the decrease in SST exceeds 1.0°C. However, the effects of this problem are restricted within shallow coastal areas and do not involve positive feedback

北太平洋亜寒帯前線の十年規模変動に対する大気応答の季節性

日本気象学会2011年度春季大会（2011年5月18日～21日, 国立オリンピック記念青少年総合センター） / 発表番号: B30

北太平洋亜寒帯前線の十年規模変動 : 変動機構と大気循環場の応答

要旨 ; 2012年度日本海洋学会春季大会（2012年3月26日～30日, 筑波大学） ; シンポジウムE「黒潮・親潮とその続流域での海洋変動と大気海洋相互作用