Minimization of atmospheric water vapor and surface emittance effects on remotely sensed sea-surface temperatures

Abstract Stratospheric water vapor concentrations and age of air are investigated in an ensemble of coupled chemistry-climate model simulations covering the period from 1960 to 2005. Observed greenhouse gas concentrations, halogen concentrations, aerosol amounts, and sea surface temperatures are all specified in the model as time-varying fields. The results are compared with two experiments (time-slice runs) with constant forcings for the years 1960 and 2000, in which the sea surface temperatures are set to the same climatological values, aerosol concentrations are fixed at background levels, while greenhouse gas and halogen concentrations are set to the values for the relevant years. The time-slice runs indicate an increase in stratospheric water vapor from 1960 to 2000 due primarily to methane oxidation. The age of air is found to be significantly less in the year 2000 run than the 1960 run. The transient runs from 1960 to 2005 indicate broadly similar results: an increase in water vapor and a decrease in age of air. However, the results do not change gradually. The age of air decreases significantly only after about 1975, corresponding to the period of ozone reduction. The age of air is related to tropical upwelling, which determines the transport of methane into the stratosphere. Oxidation of increased methane from enhanced tropical upwelling results in higher water vapor amounts. In the model simulations, the rate of increase of stratospheric water vapor during the period of enhanced upwelling is up to twice the long-term mean. The concentration of stratospheric water vapor also increases following volcanic eruptions during the simulations.

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Decadal change in summer precipitation over the east of Northwest China and its associations with atmospheric circulations and sea surface temperatures

10.5194/egusphere-egu2020-18819 ◽

2020 ◽

Author(s):

Shasha Shang ◽

Gaofeng Zhu ◽

Ruolin Li ◽

Jie Xu ◽

Juan Gu ◽

...

Keyword(s):

Water Vapor ◽

Summer Precipitation ◽

Northwest China ◽

Vapor Transport ◽

Sea Surface ◽

Water Vapor Transport ◽

Northwest Pacific ◽

Sea Surface Temperatures ◽

Surface Temperatures ◽

Decadal Variations

<p>As global warming has progressed, precipitation patterns over arid Northwest China have undergone significant change. In this study, changes in summer (JJA) precipitation over the eastern part of Northwest China (ENWC) from 1980 to 2014 were investigated using the China gridded monthly precipitation dataset (CN05.1). The results showed that summer precipitation over the ENWC experienced a decadal wet-to-dry shift in 1998. Westerlies played an important role in the upper atmospheric levels in terms of water vapor transport; the decadal variations in summer precipitation were principally controlled by the water vapor input from the ENWC's western boundary. In addition, the decadal variations in summer precipitation in the ENWC appear to be associated with a meridional teleconnection around 110&#176;E and a zonal pattern over 45&#8211;60&#176;N in the lower troposphere. These two teleconnections led to cyclonic anomalies in the ENWC and enhanced water vapor transport into the ENWC, resulting in above-normal precipitation during the 1989&#8211;1998 decadal period. Further, the warmer (colder) sea surface temperatures (SSTs) observed in the tropical Eastern Pacific correspond to the southward (northward) displacement of the Asian jet stream and a negative (positive) phase of the Silk Road pattern, resulting in a wet (dry) ENWC. Moreover, the SST anomalies in the North Atlantic and Northwest Pacific may affect summer precipitation over the ENWC via a zonal teleconnection in the middle troposphere. Details about the results will be presented in the conference.</p>

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