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      • GHRC has worked with NASA's Hurricane Science Research Program (HSRP) since the 1990's. We are the archive and distribution center for data collected during HSRP field campaigns, as well as the recent Hurricane Science and Severe Storm Sentinel (HS3) Earth Venture mission. Field campaigns provide for intensive observation of specific phenomena using a variety of instruments on aircraft, satellites and surface networks.

        GHRC also hosts a database of Atlantic and Pacific tropical storm tracks derived from the storm data published by the National Hurricane Center (NHC).
    • HS3 (2012-14)
      • Hurricane and Severe Storm Sentinel (HS3) is an Earth Ventures – Suborbital 1 mission aimed at better understanding the physical processes that control hurricane intensity change, addressing questions related to the roles of environmental conditions and internal storm structures to storm intensification.

        A variety of in-situ, satellite observations, airborne data, meteorological analyses, and simulation data were collected with missions over the Atlantic in August and September of three observation years (2012, 2013, 2014). These data are available at GHRC beginning in 2015.
    • GRIP (2010)
      • The Genesis and Rapid Intensification Processes (GRIP) experiment was a NASA Earth science field experiment in 2010 that was conducted to better understand how tropical storms form and develop into major hurricanes.

        The GRIP deployment was 15 August – 30 September 2010 with bases in Ft. Lauderdale, FL for the DC-8, at Houston, TX for the WB-57, and at NASA Dryden Flight Research Facility, CA for the Global Hawk.
    • TC4 (2007)
      • The NASA TC4 (Tropical Composition, Cloud and Climate Coupling) mission investigated the structure and properties of the chemical, dynamic, and physical processes in atmosphere of the tropical Eastern Pacific.

        TC4 was based in San Jose, Costa Rica during July 2007.

        The Real Time Mission Monitor provided simultaneous aircraft status for three aircraft during the TC4 experiment. During TC4, the NASA ER-2, WB-57 and DC-8 aircraft flew missions at various times. The science flights were scheduled between 17 July and 8 August 2007.
    • NAMMA (2006)
      • The NASA African Monsoon Multidisciplinary Analyses (NAMMA) campaign was a field research investigation based in the Cape Verde Islands, 350 miles off the coast of Senegal in west Africa.

        Commenced 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.
    • TCSP (2005)
      • The Tropical Cloud Systems and Processes (TCSP) mission was an Earth science field research investigation focused on the study of the dynamics and thermodynamics of precipitating cloud systems and tropical cyclones. TCSP was conducted during the period July 1-27, 2005 out of the Juan Santamaria Airfield in San Jose, Costa Rica.

        The TCSP field experiment flew 12 NASA ER-2 science flights, including missions to Hurricanes Dennis and Emily, Tropical Storm Gert and an eastern Pacific mesoscale complex that may possibly have further developed into Tropical Storm Eugene.
    • ACES (2002)
      • The Altus Cumulus Electrification Study (ACES) was aimed at better understanding the causes and effects of electrical storms.

        Based at the Naval Air Station Key West in Florida, researchers in August 2002 chased down thunderstorms using an uninhabited aerial vehicle, or "UAV", allowing them to achieve dual goals of gathering weather data safely and testing new aircraft technology. This marked the first time a UAV was used to conduct lightning research.
    • CAMEX-4 (2001)
      • The Convection And Moisture EXperiment (CAMEX) was a series of NASA-sponsored hurricane science field research investigations. The fourth field campaign in the CAMEX series (CAMEX-4) was held in 16 August - 24 September, 2001 and was based out of Jacksonville Naval Air Station, Florida.

        CAMEX-4 was focused on the study of tropical cyclone (hurricane) development, tracking, intensification, and landfalling impacts using NASA-funded aircraft and surface remote sensing instrumentation.
    • CAMEX-3 (1998)
      • The Convection And Moisture EXperiment (CAMEX) is a series of hurricane science field research investigations sponsored by NASA. The third field campaign in the CAMEX series (CAMEX-3) was based at Patrick Air Force Base, Florida from 6 August - 23 September, 1998.

        CAMEX-3 successfully studied Hurricanes Bonnie, Danielle, Earl and Georges, yielding data on hurricane structure, dynamics, and motion. CAMEX-3 collected data for research in tropical cyclone development, tracking, intensification, and landfalling impacts using NASA-funded aircraft and surface remote sensing instrumentation.
    • GPM Ground Validation
      • The NASA Global Precipitation Measurement Mission (GPM) Ground Validation (GV) program includes the following field campaigns:

        a) LPVEx, Gulf of Finland in autumn 2010, to study rainfall in high latitude environments

        b) MC3E, cental Oklahoma spring and early summer 2011, to develop a complete characterization of convective cloud systems, precipitation and the environment

        c) GCPEx, Ontario, Canada winter of 2011-2012, direct and remove sensing observations, and coordinated model simulations of precipitating snow.

        d) IFloodS, Iowa, spring and early summer 2013, to study the relative roles of rainfall quantities and other factors in flood genesis.

        e) IPHEx, N. Carolina Appalachians/Piedmont region May-June 2014, for hydrologic validation over varied topography.

        f) OLYMPEx, Washington's Olympic Peninsula scheduled November 2015-February 2016, for hydrologic validation in extreme coastal and topographic gradients
    • OLYMPEX (Upcoming)
      • The OLYMPEX field campaign is scheduled to take place between November, 2015, and February, 2016, on the Olympic Peninsula in the Pacific Northwest of the United States.

        This field campaign will provide ground-based validation support of the Global Precipitation Measurement (GPM) satellite program that is a joint effort between NASA and JAXA.

        As for all GPM-GV campaigns, the GHRC will provide a collaboration portal to help investigators exchange planning information and to support collection of real-time data as well as mission science, project and instrument status reports during the campaign.
    • IPHEx (2014)
      • The Integrated Precipitation and Hydrology Experiment (IPHEx) was conducted in North Carolina during the months of April-June, 2014.

        IPHEx sought to characterize warm season orographic precipitation regimes, and the relationship between precipitation regimes and hydrologic processes in regions of complex terrain.
    • IFLOODs (2013)
      • The Iowa Flood Studies (IFloodS) experiment was conducted in the central to northeastern part of Iowa in Midwestern United States during the months of April-June, 2013.

        IFloodS' primary goal was to discern the relative roles of rainfall quantities such as rate and accumulation as compared to other factors (e.g. transport of water in the drainage network) in flood genesis.
    • GCPEX (2011-2012)
      • The GPM Cold-season Precipitation Experiment (GCPEx) occurred in Ontario, Canada during the winter season (Jan 15- Feb 26) of 2011-2012.

        GCPEx addressed shortcomings in GPM snowfall retrieval algorithm by collecting microphysical properties, associated remote sensing observations, and coordinated model simulations of precipitating snow. Collectively the GCPEx data set provides a high quality, physically-consistent and coherent data set suited to the development and testing of GPM snowfall retrieval algorithm physics.
    • MC3E (2011)
      • The Mid-latitude Continental Convective Clouds Experiment (MC3E) took place in central Oklahoma during the April–June 2011 period.

        The overarching goal was to provide the most complete characterization of convective cloud systems, precipitation, and the environment that has ever been obtained, providing constraints for model cumulus parameterizations and space-based rainfall retrieval algorithms over land that had never before been available.
    • LPVEx (2010)
      • The Light Precipitation Evaluation Experiment (LPVEx) took place in the Gulf of Finland in September and October, 2010 and collected microphysical properties, associated remote sensing observations, and coordinated model simulations of high latitude precipitation systems to drive the evaluation and development of precipitation algorithms for current and future satellite platforms.

        In doing so, LPVEx sought to address the general lack of dedicated ground-validation datasets from the ongoing development of new or improved algorithms for detecting and quantifying high latitude rainfall
  • Projects
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      • Hurricane and Severe Storm Sentinel (HS3) is an Earth Ventures – Suborbital 1 mission aimed at better understanding the physical processes that control hurricane intensity change, addressing questions related to the roles of environmental conditions and internal storm structures to storm intensification.
      • DISCOVER was funded by NASA’s MEaSUREs program to provide highly accurate, multi-decadal geophysical products derived from satellite microwave sensors.
    • LIS Mission
      • Lightning observations from the Lightning Imaging Sensors (LIS) aboard the NASA’s TRMM satellite and International Space Station, as well as airborne observations and ground validation data.
    • SANDS
      • The SANDS project addressed Gulf of Mexico Alliance priority issues by generating enhanced imagery from MODIS and Landsat data to identify suspended sediment resulting from tropical cyclones. These tropical cyclones have significantly altered normal coastal processes and characteristics in the Gulf region through sediment disturbance.
      • The Land, Atmosphere Near real-time Capability for EOS (LANCE) system provides access to near real-time data (less than 3 hours from observation) from AIRS, AMSR2, MLS, MODIS, and OMI instruments. LANCE AMSR2 products are generated by the AMSR Science Investigator-led Processing System at the GHRC.
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Guide Documents

Dataset PI Documents

Dataset Software

CAMEX-3 JPL Laser Hygrometer

Table of Contents

File Naming convention
Data Format
Contact Information


A hygrometer is an instrument which determines the water vapor content of a parcel of air. Direct measurement of water vapor content has been difficult until fairly recently. Historically, typical hygrometers determined the water vapor content of the atmosphere indirectly by measuring the wet bulb temperature (e.g. a psychrometer) or the dewpoint (e.g. using a chilled mirror dewpoint hygrometer).  Determination of water vapor content is a simple matter with either.

Laser hygrometers measure the amount of water vapor directly via absorption of laser light. If the initial strength of the laser and the path length through which it travels is known, measuring the diminution of its intensity will give an indication of the amount of water vapor present.

The JPL Laser Hygrometer uses this open-path principle. A tunable diode laser operating at 1.37mm is mounted as shown in a window blank (an aluminum panel which replaces the passenger window) on the right side (FS 490 right) of the NASA DC-8. The laser and detector are mounted on a circular aluminum disk visible in the upper rectangular 'arm' of the instrument. Exactly 25cm away (on the top side of the triangular shaped blue 'arm' ) is a 0.5 inch diameter mirror. This gives a path length of 50cm- from the laser, down to the mirror and back to the detector. The strut between the 'arms' insures that the path length remains constant in spite of vibrations occurring in the instrument and the length of the arms insures that the instrument is well outside the boundary layer of the aircraft minimizing effects of the aircraft itself upon the measurements. Software in the instrument determines the water vapor content of the atmosphere from a 2 second integrated sample. The laser is normally configured for 1 Hz sampling, but can be adjusted (via software) to a maximum of 8 Hz. Measurement precision is +0.05ppmv (parts per million volume) in the stratosphere.

File Naming Convention

File names appear as: 98ddd_JPLhyg.txt where ddd is the day of the year. As the txt extension would indicate, these data are in ascii form, and appear as below.

Data Format

The data is in ASCII text form, and is comprised of two sections. The first section, the  header, contains information about the date of the data, processing date, and unit designations for each of the data columns. Below is an example of the header data. To the right of several of the rows are key letters in red that reference columns in the following data table (table 2).

Table 1. Header
25   1001
May, Randy
JPL Laser Hygrometer 
1   1
1998 08 06   1998 08 14     [Flight Date     Process Date]
Elapsed UT seconds from 0 hours on takeoff date<----------A
1.0e-6 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
99999 99999 99999 99999 99999 99999 99999 99999 99999 
H2O volume mixing ratio<----------------------------------B
Static Pressure (mb), from MMS<---------------------------C
Static Temperature (K) from MMS<--------------------------D
H2O partial pressure (mb)<--------------------------------E
Dew point temperature (C)<--------------------------------F
Saturation v.p. with respect to H2O (mb)<-----------------G
Saturation v.p. with respect to ice (mb)<-----------------H
Relative Humidity (%, relative to H2O sat.)<--------------I
grams H2O per kilogram of air<----------------------------J
JPL Laser Hygrometer. ** Preliminary Data **

Note that on the next to last line is the phrase "** Preliminary Data **". These data were processed either during or immediately following the CAMEX-3 experiment. They were NOT reprocessed subsequent to that time as post flight calibrations were consistent with pre-mission values. Conversation with the instrument PI, Dr. Randy May at JPL, confirmed that these data were in final form.

By using the key for each data column from the above table, decoding the data becomes trivial. Mixing ratio, presented as parts per million by volume, are given in column B, which is the most common unit used for stratospheric measurements where this type of instrument was first utilized (for the NASA ER-2 during the 1997 POLARIS mission). That value is shown in column J.

Table 2. Data
    A                B             C          D             E              F              G                H            I        J 

   UT(s)       ppmv      P(mb)    T(K)      Ep(mb)       Td(C)    Esh(mb)    Esi(mb)    %RH  g/kg 
 63428.0   157.87  403.60 255.50   0.06372  -49.85   1.53137   1.28993   4.16  0.0987 
 63430.0   157.66  403.00 255.40   0.06354  -49.85   1.51846   1.27783   4.18  0.0985 
 63432.0   156.96  402.40 255.30   0.06316  -49.95   1.50566   1.26584   4.19  0.0981 
 63434.0   155.21  401.80 255.20   0.06236  -50.05   1.49295   1.25395   4.18  0.0970 
 63436.0   153.99  401.10 255.10   0.06177  -50.15   1.48034   1.24217   4.17  0.0962 
 63438.0   153.53  400.60 255.00   0.06151  -50.15   1.46782   1.23048   4.19  0.0960 
 63440.0   153.80  399.90 254.90   0.06150  -50.15   1.45540   1.21889   4.23  0.0961 
 63442.0   154.01  399.30 254.70   0.06150  -50.15   1.43084   1.19602   4.30  0.0963 
 63443.0   153.69  399.00 254.70   0.06132  -50.15   1.43084   1.19602   4.29  0.0961 
 63445.0   153.42  398.40 254.60   0.06112  -50.15   1.41870   1.18474   4.31  0.0959 
 63447.0   153.32  397.70 254.50   0.06097  -50.25   1.40664   1.17355   4.33  0.0958 
 63449.0   153.72  397.00 254.40   0.06103  -50.25   1.39469   1.16245   4.38  0.0961


See "Open-Path, Near-IR Tunable Diode Laser Spectrometer for Atmospheric Measurements of H2O", R.D. May, J. Geophys. Res., 103, 19,161-19,172 (1998).

Contact Information

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

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Phone: 256-961-7932




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