Comparison of Wind and Wave Fields between High-Resolution Simulations and Operational Forecast Products : A Case of Wave Development under Easterly Wind Jets in the West of the Tsugaru Strait

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Estimation of cool summer damage in the Tohoku region based on the MRI AGCM

We analyzed the impact of climate change due to global warming on the risk of cool summer damage to paddy rice in the Tohoku region of Japan. We downscaled the atmospheric general circulation model of the Meteorological Research Institute(MRI AGCM) to 10 km, and we used monthly average temperatures and their standard deviations to correct the bias of the simulated temperatures. We did not use daily averaged temperatures to determine the risk of cool summer damage. Instead, we used the cooling degree calculated from the average daily temperature over a period of time(CDAT). We also used the standardized yield calculated from temperatures during the month preceding beading. An examination of the reproducibility of cooling damage occurring under the current climate was based on bias-corrected data which revealed that although the simulated risk of cool summer damage slightly underestimated both the CDAT and the standardized yield, the areal distributions of risk were similar to those in years of cool summer damage. We assumed that the heading stage occurred 15.6 days earlier than current climate because of the impact of temperature increase under the future climate and therefore calculated the CDAT and standardized yield by advancing the critical period by half a month. During the second- and third-coolest summers under the future climate scenario, the risk of cool summer damage decreased in the southern Tohoku region facing the Pacific Ocean and inAomori Prefecture on the Japan Sea side, but the risk of cool summer damage was almost the same as during the observed cool summer of 1980. In summary, our results revealed that under a future climate, simulated by the MRI AGCM, the risk of cool summer damage will persist in the Tohoku region; risk management for cool summer damage will therefore be essential, even though global temperatures rise

Global analysis of the pressure adjustment mechanism over sea surface temperature fronts using AIRS/Aqua data

We investigate the signatures of atmospheric pressure adjustment mechanism for surface wind convergence/divergence over major sea surface temperature (SST) frontal regions using global observations of satellite sounding and scatterometer. Lower tropospheric air thickness, which includes a sea-level pressure component modified by air temperature in the marine atmospheric boundary layer, is analyzed, and the relation between the Laplacian of the thickness and wind convergence are examined. Among four SST frontal regions in mid-latitudes, correlation between the thickness Laplacian and wind convergence is the largest over the Gulf Stream followed by those for the Agulhas Return Current and for the Brazil/Malvinas Current, and relatively small but still significant over the Kuroshio-Oyashio Extension. These correlations strongly suggest that the pressure adjustment mechanism ubiquitously plays an important role in air-sea interaction over the global SST frontal regions. Furthermore, air temperatures in the first two regions exhibit SST-relating signatures even in the mid-troposphere

Diurnal Variation of Surface Wind Divergence in the Maritime Continent Using ASCAT and SeaWinds Observations and ERA5 Reanalysis Data

This study investigates the diurnal variation of surface wind divergence in the seas of the Maritime Continent by using satellite scatterometer observations and atmospheric reanalysis data. This is the first study to demonstrate the distribution and seasonal variation of the diurnally varying surface winds in the Maritime Continent in terms of wind divergence. Wind divergence develops from the coasts of the islands toward the center of the seas and dominates during the afternoon and evening hours. Wind convergence dominates over the seas during the nighttime and morning hours. The offshore extensions of the wind divergence and convergence from the coast differ regionally and thus show the asymmetric patterns with respect to the center of the seas. In particular, strong wind divergence develops from the southern coasts of the Java Sea and the Arafura Sea to extend northward beyond the center of the seas. The diurnal amplitudes of wind divergence vary seasonally and reach a peak in September in most of the seas. The switching times between wind divergence and convergence are almost fixed throughout the year regardless of the monsoon reversal