Diurnal Variation in Cloud Liquid Water Path Derived from Five Cross-Track Microwave Radiometers Onboard Polar-Orbiting Satellites

Lin Lin,Xiaolei Zou

doi:10.3390/rs12142177

Abstract

The Advanced Microwave Sounding Unit (AMSU)-A/Advanced Technology Microwave Sounder (ATMS) onboard the National Oceanic Atmospheric Administration (NOAA)-18/-19, MetOp-A/-B, and Suomi National Polar-orbiting Partnership satellites provide global observations of the cloud Liquid Water Path (LWP) almost 10 times a day. This study explores the possibility of capturing the diurnal cycle of the LWP. An inter-satellite cross-calibration is first carried out using a double-difference method. A remapping is then used to obtain the AMSU-A-like LWP to account for beam shape discrepancies between the ATMS and AMSU-A. We finally examine the diurnal cycle of the LWP over the Southeast Pacific Ocean using the ATMS and AMSU-A data from the five satellites mentioned above. Results show that the remapped ATMS results agree well with the AMSU-A results at the same local time over a stratocumulus region. LWP retrievals from multiple satellite cross-track microwave radiometers can well reproduce the diurnal variation characteristics of LWP in 2015 over the East Pacific Ocean, including the seasonal variation of the diurnal variation. This study presents the first step toward merging LWP data from all ATMS and AMSU-A radiometers and will be of interest to many researchers studying LWP-related weather and climate changes, especially considering the possible loss of higher-resolution microwave-frequency conical-scanning sensors in the coming years.

Highlights

Changes in cloud parameters, such as the Liquid Water Path (LWP), on regional, and perhaps even global scales, are associated with cloud feedback mechanisms in the climate system
Wood et al [1] investigated the diurnal cycle of LWP over the subtropical and tropical oceans using the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) satellite microwave radiometer data from 1999 and 2000
Polar-orbiting Operational Environmental Satellites (POES) cross-track microwave radiometers have provided more than 20 years of global oceanic cloud LWP data since the launch of the National Oceanic Atmospheric Administration (NOAA)-15 in 1998 carrying the Advanced Microwave Sounding Unit (AMSU)-A

Summary

Introduction

Changes in cloud parameters, such as the Liquid Water Path (LWP), on regional, and perhaps even global scales, are associated with cloud feedback mechanisms in the climate system. Polar-orbiting Operational Environmental Satellites (POES) cross-track microwave radiometers have provided more than 20 years of global oceanic cloud LWP data since the launch of the National Oceanic Atmospheric Administration (NOAA)-15 in 1998 carrying the Advanced Microwave Sounding Unit (AMSU)-A. With the ATMS onboard the next-generation JPSS operational satellite series in the United States, and the AMSU-A and MHS onboard MetOp-A, -B, and -C from the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT), the time series of global microwave measurements can be further extended to well beyond 2028 This offers an opportunity to study climate using a long time series of AMSU-A/ATMS observations. 2020, 12, 2177 climate data records of LWP over global oceans based on POES cross-track microwave radiometers AMSU-A and ATMS.

Some Characteristic Differences between AMSU-A and ATMS

The ATMS Remapping Algorithm

Diurnal Variation Calculation

Results of ATMS LWP Derived with and without the Remapping