Diurnal Variation Characteristics Of Temperature And Climate Change Trends Of Cloud-water Paths Based On Microwave Thermometers

Meteorological data are the basis of weather and climate research.However,in the inaccessible plateau and vast ocean surface,climate research has been limited by the shortage of observation data.Meteorological satellites provide observation data with global coverage for climate research.Microwave Sounder is the oldest microwave instrument onboard meteorological satellites.Microwave Sounder can not only provide data for the study of diurnal variation of surface temperature in Plateau and ocean areas where conventional observation data are insufficient,but also provide observation information of cloud water in the atmosphere.Based on the multi-year brightness temperature observation data of the microwave thermometer AMSU-A(Advanced Microwave Sounding Unit-A)on the polar orbiting satellites NOAA-15,NOAA-18,NOAA-19 and Met Op-A,taking advantage of the different characteristics of different polar orbiting satellites in the local equator crossing time,the hourly surface channel brightness temperature in the Qinghai-Tibet Plateau was established by the Fourier fitting method in this study.Combining the historical observations from Maqu Station and the latest ERA5 hourly reanalysis data,the ability of satellite brightness temperature data to reproduce the characteristics of diurnal surface air temperature changes in the Qinghai-Tibet Plateau and Pacific Ocean are analyzed.Based on the multi-year brightness temperature observation data of microwave thermometer AMSU-A on polar orbiting satellite NOAA-15,the paper also establishes the cloud liquid water path inversion products on the global ocean,and analyzes the climate change characteristics of the multi-year cloud water path inversion data on the Pacific Ocean.The results show that,compared with the ERA5 data,the satellite brightness temperature data can better reproduce the diurnal variation characteristics of the surface air temperature in the Pacific Ocean and Maqu station area of the Qinghai-Tibet Plateau,and can also better reflect the seasonal difference in the diurnal variation of the temperature.Comparing the satellite brightness temperature data with the station observation data,it is found that the daily variation characteristics of spring and summer have the best corresponding relationship,and the minimum temperature difference in winter is relatively large.We compared the diurnal seasonal differences of the four main vegetation types on the plateau,and found that both seasons and vegetation types have a significant impact on the diurnal phase of surface temperature.The time when the daily maximum temperature appears on the ocean is obviously earlier than the other three seasons in winter,while the time when the daily minimum temperature appears obviously lags behind in spring.The diurnal variation range of brightness temperature in the Pacific has obvious spatial distribution characteristics and seasonal variation characteristics.The CLWP(Cloud Liquid Water Path)inversion data can well reproduce the average spatial distribution characteristics of the years and the corresponding climate change trend.The CLWP climate trend shows obvious latitude zone characteristics,and the increasing and decreasing trends appear with the latitude zone interval.Moreover,in the eastern Pacific region of the northern hemisphere,the latitude zone characteristic of the climatic trend of the CLWP has a phenomenon of migration northward.In contrast,the climatic trend of the inversion product has better similarity with the ERA5 reanalysis data.While the latitude zone characteristics of the trend,especially the northward movement of the latitude zone characteristics,cannot be reproduced well by the FNL data.It is characterized by a decrease in water vapor in the equatorial region,and a significant increase in cloud liquid water paths on both sides.