Title: MODIS comparisons with northeastern Pacific in situ stratocumulus microphysics

Abstract

Abstract Vertical sounding measurements within stratocumuli during two aircraft field campaigns, Marine Stratus/stratocumulus Experiment (MASE) and Physics of Stratocumulus Top (POST), are used to validate Moderate Resolution Imaging Spectroradiometer (MODIS) cloud optical thickness (COT), cloud liquid water path (LWP), and cloud effective radius ( r _e ). In situ COT, LWP, and r _e were calculated using 5 m vertically averaged droplet probe measurements of complete vertical cloud penetrations. MODIS COT, LWP, and r _e 1 km pixels were averaged along these penetrations. COT comparisons in POST showed strong correlations and a near 1:1 relationship. In MASE, comparisons showed strong correlations; however, MODIS COT exceeded in situ COT, likely due to larger temporal differences between MODIS and in situ measurements. LWP comparisons between two cloud probes show good agreement for POST but not MASE, giving confidence to POST data. Both projects provided strong LWP correlations but MODIS exceeded in situ by 14–36%. MODIS in situ r _e correlations were strong, but MODIS 2.1 µm r _e exceeded in situ r _e , which contributed to LWP bias; in POST, MODIS r _e was 20–30% greater than in situ r _e . Maximum in situ r _e near cloud top showed comparisons nearer 1:1. Othermore » MODIS r _e bands (3.7 µm and 1.6 µm) showed similar comparisons. Temporal differences between MODIS and in situ measurements, airplane speed differences, and cloud probe artifacts were likely causes of weaker MASE correlations. POST COT comparison was best for temporal differences under 20 min. POST data validate MODIS COT but it also implies a positive MODIS r _e bias that propagates to LWP while still capturing variability.« less

Authors:

Noble, Stephen R. ^[1]; Hudson, James G. ^[1]

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+ Show Author Affiliations

1. Desert Research Institute Nevada System of Higher Education Reno Nevada USA

Publication Date:

Tue Aug 18 00:00:00 EDT 2015

Research Org.:

Univ. of Nevada, Reno, NV (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1221674

Alternate Identifier(s):

OSTI ID: 1221675; OSTI ID: 1454437

Grant/Contract Number:  

DE‐FG02‐05ED63999; DE‐SC0009162; SC0009162

Resource Type:

Published Article

Journal Name:

Journal of Geophysical Research: Atmospheres

Additional Journal Information:

Journal Name: Journal of Geophysical Research: Atmospheres Journal Volume: 120 Journal Issue: 16; Journal ID: ISSN 2169-897X

Publisher:

American Geophysical Union (AGU)

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; remote sensing validation; stratocumulus optical depth; stratocumulus effective radius; cloud liquid water path; northeastern Pacific stratocumulus; cloud microphysics