NAMMA Cloud Microphysics (CAPS-PIP)

Table of Contents

This data set consists of in-situ cloud microphysics data collected from two instruments mounted on the NASA DC-8 aircraft:

1. The Cloud, Aerosol, and Precipitation Spectrometer (CAPS) is a combination of two probes: the Cloud Imaging Probe (CIP), used for two-dimensional images and size distributions nominally between 25 and 1550 µm, and the Cloud and Aerosol Spectrometer (CAS), which uses forward-scatter and back-scatter techniques to measure particle size distributions between 0.35 and 50 µm.
2. The Precipitation Imaging Probe (PIP) is an optical spectrometer which measures the size and shape of particles from 100µm to 6200µm. 

This data set includes the combined particle size distributions and a small sample of images from each probe. A Readme file provided by the data producer explains the dataset  in detail, and can be found here: ftp://ghrc.nsstc.nasa.gov/pub/doc/namma/namcaps/NAMMA_Cloud_Microphysics_readme.txt

These data files were generated during support of the NASA African Monsoon Multidisciplinary Analyses (NAMMA) campaign, a field research investigation sponsored by the Science Mission Directorate of the National Aeronautics and Space Administration (NASA). This mission was based in the Cape Verde Islands, 350 miles off the coast of Senegal in west Africa. Commencing in August 2006, NASA scientists employed surface observation networks and aircraft to characterize the evolution and structure of African Easterly Waves (AEWs) and Mesoscale Convective Systems over continental western Africa, and their associated impacts on regional water and energy budgets. For more information about the NAMMA Campaign, go to the NAMMA web site: http://namma.nsstc.nasa.gov/

Cloud, Aerosol, and Precipitation Spectrometer (CAPS):  

This multipurpose particle spectrometer is five instruments packaged into a single integrated measurement system that provides aerosol particle and cloud hydrometeor size distributions from 0.5 to 50 um, particle shape (discrimination between water and ice), particle optical properties (refractive index), precipitation size distributions from 25 um to 1550 um, liquid water content from 0.01 to 3 gm-3 and aircraft velocity and atmospheric temperature and pressure. This instrument replaces PMS Inc.'s FSSP-100, FSSP-300, 2D-C, 2D-P and KLWC.
The CAPS has two optical sensors to derive the size of individual particles: 1) the cloud imaging probe (CIP) and 2) the cloud aerosol spectrometer (CAS).

Cloud Imaging Probe (CIP):  

This optical spectrometer measures the size and shape of particles passing through its collimated laser beam, from 25µm to 1550 µm, liquid water content from 0.01 to 3 gm-3 and airspeed to 200 ms-1. It uses a fast 64-element photodiode array to generate 2-Dimensional Images of the particles,as well as sizing in 1-Dimensional Histogram form. Included in this instrument package are temperature, pressure and relative humidity sensors.

Cloud aerosol Spectrometer (CAS):

The CAS collects the light scattered in the forward direction (4-12 °) by particles passing through a focused laser beam and converts the light intensity to a particle diameter between 0.5 and 50 mm using Mie light scattering theory. The CAS also measures backscattered light (168-176 °) in order to derive particle refractive index (Baumgardner et al., 1996) and shape factors (Baumgardner et al., 2004). Three pieces of information are recorded by the CAS about each particle: 1) the forward scattered light intensity, 2) backward scattered light intensity, and 3) the time between each particle. The particle by particle information is used to derive size distributions, particle refractive index and shapes, and concentration fluctuations at scales of a meter or less.

Precipitation Imaging Probe (PIP):

This optical spectrometer measures the size and shape of particles from 100µm to 6200µm. It is the classic airborne 2-Dimensional imaging probe, with the expanded capability of the 64-element diode array and fast Digital Signal Processing electronics. The probe resolution is 100µm with a particle sizing range of 6.2mm. Sample area is 26cm x 6.2mm. Maximum airspeed: 200m/s.

The CIP and PIP are both two-dimensional optical array probes which record images of particles that travel through their lasers. The CIP has a resolution of 25 microns per pixel and the PIP has a resolution of 100 microns per pixel. The recorded images are then analyzed to produce a particle size distribution from 25 microns to 3 centimeters. The CIP is used for particles smaller than 1000 microns and the PIP is used for all larger particles. The CAS probe measures particle size distributions from 0.55 to 52.5 microns. It uses a forward-scattering measurement technique. These probes are manufactured by Droplet Measurement Technologies, and additional information can be found here: http://www.dropletmeasurement.com/

Example data files are:

namma_caps_yyyymmdd_2D_psd.txt
namma_caps_yyyymmdd_CAS_psd.txt

Example Browse files are:

namma_caps_yyyymmdd_tttttt_CIP10.png
namma_caps_yyyymmdd_tttttt_PIP.png

where,

namma_caps  - Represents the NAMMA project and the CAPS-PIP instruments
yyyymmdd  - Is the year, month and date of the flight
2D - Indicates data is from the 2D probes (CIP & PIP)
CAS  - Indicates data is from the Cloud and Aerosol Spectrometer
psd - Shows that these are partial size distributions
tttttt - UTC time
CIP10 - Images from the Cloud Imaging Probe
PIP - Images form the Precipitation Imaging Probe

These data files are in ASCII, tab delimited, format and can be easily viewed with most web browsers. An example of the data format from the CAS and the 2D probes are shown below. The concentrations are binned into 30 bins, and not all are shown in these examples.

CAS:

Time       Nt(#/m3)       LWC(g/m3)       Concentration(m^-4)
--------------------------------------------------------------------------------
42900     9.99e+30     9.99e+30            9.99e+30     9.99e+30     9.99e+30     9.99e+30     9.99e+30 .........

2D probes:

Time       Nt(#/m3)       IWC(g/m3)          Concentration(m^-4)
--------------------------------------------------------------------------------
42900     0.00e+00     0.00e+00            0.00e+00     0.00e+00     0.00e+00     0.00e+00     0.00e+00 .........

Column headers are described as follows:

TIME - Elapsed UTC seconds from 0 hours on day of flight

Nt(#/m3) - Total concentration

LWC(g/m3) - Liquid water content

IWC(g/m3) - Condensed water content from CIP integration

Concentration(m^-4) - Particle number concentration normalized by bin width

Additional information on file content and structure can be found in each file header.

Baumgardner, D., J.E. Dye, B. Gandrud, K. Barr, K. Kelly, K.R. Chan, 1996: Refractive indices of aerosols in the upper troposphere and lower stratosphere, Geophys. Res. Lett, 23, 749-752.

Baumgardner, D., H. Jonsson, W. Dawson, D. O’Connor and R. Newton, 2002: The cloud, aerosol and precipitation spectrometer (CAPS): A new instrument for cloud investigations, Atmos. Res., 59-60, 251-264.

The data producer is:

Andrew Heymsfield
National Center for Atmospheric Research
heyms1@ucar.edu

To order these data or for further information, please contact:

Global Hydrology Resource Center
User Services
320 Sparkman Drive
Huntsville, AL 35805
Phone: 256-961-7932
E-mail: support-ghrc@earthdata.nasa.gov
Web: http://ghrc.nsstc.nasa.gov/