Diurnal variations of humidity and ice water content in the tropical upper troposphere
Journal article, 2010

Observational results of diurnal variations of humidity from Odin-SMR and AURA-MLS, and cloud ice mass from Odin-SMR and CloudSat are presented for the first time. Comparisons show that the retrievals of humidity and cloud ice from these two satellite combinations are in good agreement. The retrieved data are combined from four almost evenly distributed times of the day allowing mean values, amplitudes and phases of the diurnal variations around 200 hpa to be estimated. This analysis is applied to six climatologically distinct regions, five located in the tropics and one over the subtropical northern Pacific Ocean. The strongest diurnal cycles are found over tropical land regions, where the amplitude is ∼7 RHi for humidity and ∼50% for ice mass. The greatest ice mass for these regions is found during the afternoon, and the humidity maximum is observed to lag this peak by ∼6 h. Over tropical ocean regions the variations are smaller and the maxima in both ice mass and humidity are found during the early morning. Observed results are compared with output from three climate models (ECHAM, EC-EARTH and CAM3). Direct measurement-model comparisons were not possible because the measured and modelled cloud ice masses represent different quantities. To make a meaningful comparison, the amount of snow had to be estimated from diagnostic parameters of the models. There is a high probability that the models underestimate the average ice mass (outside the 1-σ uncertainty). The models also show clear deficiencies when it comes to amplitude and phase of the regional variations, but to varying degrees. © 2010 Author(s).

Author

Patrick Eriksson

Chalmers, Earth and Space Sciences, Global Environmental Measurements and Modelling

Bengt Rydberg

Chalmers, Earth and Space Sciences, Global Environmental Measurements and Modelling

Marston Sheldon Johnston

Chalmers, Earth and Space Sciences, Global Environmental Measurements and Modelling

Donal Murtagh

Chalmers, Earth and Space Sciences, Global Environmental Measurements and Modelling

Hamish Struthers

Stockholm University

Sylvaine Ferrachat

Swiss Federal Institute of Technology in Zürich (ETH)

U. Lohmann

Swiss Federal Institute of Technology in Zürich (ETH)

Atmospheric Chemistry and Physics

1680-7316 (ISSN) 1680-7324 (eISSN)

Vol. 10 23 11519-11533

Driving Forces

Sustainable development

Subject Categories

Aerospace Engineering

Meteorology and Atmospheric Sciences

Control Engineering

Climate Research

Roots

Basic sciences

DOI

10.5194/acp-10-11519-2010

More information

Latest update

3/19/2018