Tropospheric water vapor, convection, and climate

Abstract

[1] Recent progress is reviewed in the understanding of convective interaction with water vapor and changes associated with water vapor in warmer climates. Progress includes new observing techniques (including isotopic methods) that are helping to illuminate moisture-convection interaction, better observed humidity trends, new modeling approaches, and clearer expectations as to the hydrological consequences of increased specific humidity in a warmer climate. A theory appears to be in place to predict humidity in the free troposphere if winds are known at large scales, providing a crucial link between small-scale behavior and large-scale mass and energy constraints. This, along with observations, supports the anticipated water vapor feedback on climate, though key uncertainties remain connected to atmospheric dynamics and the hydrological consequences of a moister atmosphere. More work is called for to understand how circulations on all scales are governed and what role water vapor plays. Suggestions are given for future research.

Airborne in situ vertical profiling of HDO / H<sub>2</sub><sup>16</sup>O in the subtropical troposphere during the MUSICA remote sensing validation campaign

“…This in turn leads to the conclusion that this air mass must have originated from much higher than the sampling altitude. Descent and adiabatic warming lead to a strong decrease of relative humidity versus ice to ∼ 8 % (not shown), a process termed subsidence drying (Sherwood et al, 2010). The altitude of origin of this air mass was above 5000 m.…”

Structure and Dynamical Influence of Water Vapor in the Lower Tropical Troposphere

“…17. If the humidity at a given temperature is controlled by the humidity that the sampled air had at last saturation (Sherwood et al 2010), and there was no preferred temperature of the mid-tropospheric moisture source, we would expect T sat to be distributed between T and some minimum T characteristic of the lowest value of temperatures in the troposphere. Because tropospheric mixing is more efficient along isentropes (roughly isotherms), and air that was last saturated at much colder temperatures must have travelled a greater distance through the troposphere, T sat should be less than, but roughly follow T, as for instance for T\0 C in Fig.…”

“…The thermodynamic effect has been extensively studied over the past decades (Sherwood et al 2010), the radiative effect-especially in the lower troposphere-has not. The purpose of this article is to review our understanding, and to evaluate our ability, to remotely sense important features of the lower-tropospheric water vapor distribution.…”

Effects of Arctic geoengineering on precipitation in the tropical monsoon regions

“…Geoengineering is an intentional manipulation of the climate system to reduce the undesired impacts of climate change caused by increasing greenhouse gases (Keith 2000;Shephard et al 2009;IPCC 2014). Geoengineering by injecting sulfate aerosols into stratosphere was first suggested by Budkyo (1974).…”