Title: Regime dependence of cloud condensate variability observed at the Atmospheric Radiation Measurement Sites

Abstract

Microphysical processes and cloud–radiation interaction occur on spatial scales of variability smaller than those represented explicitly in global weather forecasting and climate models. It is therefore necessary to parametrize the unresolved heterogeneity of humidity and cloud condensate in order to predict process rates accurately. Ground‐based observations from the Atmospheric Radiation Measurement sites located in various climatic regions of the world provide a source of high‐temporal‐resolution observations of cloud condensate. A number of different retrieval products for cloud condensate are assessed for the different geographical regions, years and seasons. The retrieval reliability varies with cloud type, but for cloud categories largely unaffected by precipitation a comparison across sites and longer time periods is possible. These observations confirm previously documented variability behaviour as a function of cloud fraction, but also reveal a systematic regime dependence that is not captured by existing parametrizations. Condensate variability measured as a fractional standard deviation (FSD) in warm boundary‐layer clouds is greater in the Tropics than in mid and high latitudes for scenes with comparable cloud type and fraction, with the observed FSD varying from 1.2 in the Tropics to 0.4 in the Arctic. A parametrization of the FSD of cloud liquid condensate based on the grid‐boxmore » mean total water amount and cloud fraction is formulated and shown to capture the observed range of FSD values better across different geographical sites and different seasons. The regime dependence of FSD for cirrus cloud is less pronounced than that for liquid clouds and is found largely to agree with FSD values previously derived from satellite observations.« less

Authors:

Ahlgrimm, Maike ^[1]; Forbes, Richard M. ^[1]

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+ Show Author Affiliations

1. European Centre For Medium Range Weather Forecasts Reading UK

Publication Date:

Tue May 10 00:00:00 EDT 2016

Sponsoring Org.:

USDOE

OSTI Identifier:

1401189

Grant/Contract Number:  

DE‐SC0005259

Resource Type:

Publisher's Accepted Manuscript

Journal Name:

Quarterly Journal of the Royal Meteorological Society

Additional Journal Information:

Journal Name: Quarterly Journal of the Royal Meteorological Society Journal Volume: 142 Journal Issue: 697; Journal ID: ISSN 0035-9009

Publisher:

Wiley Blackwell (John Wiley & Sons)

Country of Publication:

United Kingdom

Language:

English