Submillimeter-wave Passive Remote Sensing of Ice Clouds

We have been developing a new technique for remote sensing ice cloud properties using passive submillimeter radiometers. This approach offers advantages over existing methods because it is fundamentally more directly sensitive to ice water path (IWP) and mean IWC weighted equivalent sphere diameter (Dme) than are infrared and visible radiometry or radar techniques.

A schematic diagram shows the submillimeter remote sensing idea for the downward viewing geometry.


A heterodyne instrument was developed at NASA Goddard Space Flight Center (GSFC) by Paul Racette and Jim Wang. The Compact Scanning Submillimeter-wave Imaging Radiometer (CoSSIR) was designed to have 15 channels with receivers at 183, 220, 380, 487, and 640 GHz. CoSSIR flew on the ER-2 during the CRYSTAL-FACE cirrus experiment in Florida in July 2002. See below for a journal article about analysis of CoSSIR data from CRYSTAL-FACE. CoSSIR was upgraded to achieve better receiver performance and flown in January 2006 in the CR-AVE deployment. CoSSIR was deployed during the TC4 experiment in July/August 2007 with receivers at 183, 220, 380, 640 (H and V pol), and 874 GHz (see talk slides below). CoSSIR has now been modified to have receivers at 183, 325, 448, 640 (H and V pol), and 874 GHz.

In the past I have been involved with two other submillimeter-wave radiometers .


A talk (1.4 MB PDF) presented at the TC4Science Team Meeting (February 28, 2008) describes analysis of CoSSIR data from TC4, including comparisons with other remote sensing instruments (Note: the agreement with the Cloud Radar System has since improved with a change in the CRS data).

A talk (580 kB PDF) prepared by myself and presented by Jim Wang at the CR-AVE Science Team Meeting (November 15, 2006) describes analysis of CoSSIR data from CR-AVE, including the 487 GHz polarization signature from oriented ice crystals in tropical anvils.

Journal Articles

A paper about a new ice cloud profile retrieval algorithm has been published in Atmospheric Measurement Techniques . It uses in situ microphysical and humidity measurements from TC4 along with CloudSat data for the a priori information, performs retrievals with CoSSIR data, and evaluates the retrievals with Cloud Radar System data from TC4.

A paper about retrievals of anvil ice cloud properties from CRYSTAL-FACE CoSSIR data and validation with the Cloud Radar System (CRS) has been published in the Journal of Applied Meteorology .

A paper describing the JPL SWCIR instrument, the Bayesian retrieval algorithm, and simulations of retrieval accuracy was published in JGR:

A paper using radiative transfer modeling to gain a detailed understanding of submillimeter cirrus remote sensing was published in the Journal of Applied Meteorology:

A paper exploring the potential of a submillimeter spectrometer for cirrus remote sensing was also published in JAM:

My work in this area started with a theoretical exploration of microwave radiative transfer in nonspherical cirrus ice crystals. Two papers were published from this portion of my PhD thesis:


A channel selection study (2003) (431 kB PDF) describes ice cloud retrieval simulations of 26 microwave channel sets with frequencies from 183 to 916 GHz and 6 sets of four infrared wavelength bands to try to determine the optimal channels for cirrus retrievals. A section of the report describes retrieval simulations for clouds with horizontally oriented particles and investigates issues of polarization.

Last modified: September 12, 2012

Back to Home