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Facilitating Access to Global Observing Systems Data and Information

GCOS Atmospheric Upper Air ECV*
Temperature

*over land, sea and ice

Definiftion: Upper-Air Observation - (Also called sounding, upper-air sounding.) A measurement of atmospheric conditions aloft, above the effective range of a surface weather observation. This is a general term, but is usually applied to those observations that are used in the analysis of upper-air charts (as opposed to measurements of upper-atmospheric quantities primarily for research). Among the elements evaluated are pressure, temperature, relative humidity (e.g., by radiosonde aircraft observations), and wind speed and direction (e.g., by rawinsonde, aircraft, or wind profiling radars). Also, some mountain stations are high enough and exposed enough so that their observations may be included in the upper-air network at their elevation. See also meteorological rocket, radiosonde balloon. (from the AMS Glossary of Meteorology)

Introduction: Specific microwave radiance data from satellites (Microwave Sounding Unit (MSU) and Advanced Microwave Sounding Unit A (AMSU-A)) have become key elements of the historical climate record and need to be continued into the future to sustain a long-term record. For climate applications, the satellite systems must be operated in adherence with the GCMPs.   Failure of an on-board AMSU-A (or equivalent) instrument should be regarded as a strong driver to launch a new satellite in the series. The new high-resolution infrared sounders such as the Atmospheric Infrared Sounder (AIRS), the IASI (Infrared Atmospheric Sounding Interferometer) and the future CrIS (Cross-Track Infrared Sounder) improve the vertical resolution of satellite-derived temperature soundings, which should significantly improve the monitoring of temperature change. Atmospheric temperature sounding data play an important role, along with radiosonde and aircraft data in reanalyses of temperature and other upper-air variables. Radiosonde temperatures form an important climate data record in their own right, albeit requiring careful homogenisation to account for instrumental and real-time processing changes. Aircraft temperatures are also prone to biases for which adjustments need to be developed by reanalysis centres.
 
GPS radio occultation (RO) measurements provide high vertical resolution profiles of atmospheric refractive index that relate directly to temperatures above about 6 km altitude (where water vapour effects are small). They provide benchmark observations that can be used to “calibrate” the other types of temperature measurement, and supplement the GRUAN in this regard. RO instruments are flown on multiple low Earth orbiting satellites. The COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) fleet of satellites provides real-time data and the GNSS Receiver for Atmospheric Sounding (GRAS) instrument is the first of a series of operational RO instruments. Real-time use of the data has been established and a positive impact on Numerical Weather Prediction (NWP) has been demonstrated. Climate applications are being developed by providing consistent time series of bending angles and refractivity profiles. The introduction of other GNSS offers opportunities for further improvement in coverage of RO data.

International Data Centers and Archives for Atmospheric Upper-Air:

Coordinating Bodies:

(Source: WMO/IOC Implementation Plan for the Global Observing System for Climate in Support of the UNFCCC (2010 Update) GCOS-138/GOOS-184/GTOS-76/WMO-TD/No. 1523)

Satellite Observations: With humidity, atmospheric temperature profile data are a core requirement for weather forecasting and are coordinated within the framework of CGMS (The Coordination Group for Meteorological Satellites). The data are used for Numerical Weather Prediction (NWP), for monitoring inter-annual global temperature changes, for identifying correlations between atmospheric parameters and climatic behaviour, and for validating global models of the atmosphere. Upper air temperatures are a key dataset for detection and attribution of tropospheric and stratospheric climate change, measured both by radiosondes and satellite instruments. Temperatures measured by high-quality radiosondes are an important reference against which satellite-based measurements can be calibrated. Upper air temperatures are important for separating the various possible causes of global change, and are vital for the validation of climate models. Infrared (HIRS) and microwave sounders (MSU and AMSU) have been providing atmospheric profiles for almost thirty years. The microwave data in particular have become key elements of the historical climate record and equivalent measurements need to be continued into the future to sustain a long-term record. The MSU radiance record is a primary resource for this, providing essential coverage over the oceans and data for comparison and combination with radiosonde data over land.

For global NWP, polar satellites provide information on temperature with global coverage, good horizontal resolution and acceptable accuracy, but improvements in vertical resolution are needed. Performance in cloudy areas has been poor, but the microwave measurements such as AMSU have provided substantial improvements. As in the case of humidity profiles, the Aqua, MetOp, NOAA and NPOESS missions offer comparable improvements in vertical resolution for measuring atmospheric temperature (using AIRS+, AMSU-A, CrIS, HIRS, IASI, MSU).

Problems with the Data Record: For regional NWP, polar orbiting satellites provide information on temperature with acceptable accuracy and good horizontal resolution, but with marginal temporal frequency and vertical resolution for mesoscale prediction. Advanced radiometers or interferometers planned for future satellites should improve on the vertical resolution and accuracy of current radiometers. Geostationary satellites provide frequent radiance data, but their use over land is hindered because of the difficulty in estimating surface emissivity. In nowcasting, the temperature and humidity fields are particularly useful for determining atmospheric stability for predicting precipitation type, the amount of frozen precipitation, and convective storms. As with humidity profiles, nowcasting predictions using atmospheric temperature data benefit from hourly geostationary infrared soundings (such as from the GOES and MSG series – with these missions now capable of providing such data at 15 minute intervals). The combination of the HIRS/3 and AMSU instruments on the NOAA and MetOp series allows improved information, sufficient to infer temperature within several thick layers in the vertical. On the MetOp series, IASI is used with other instruments to deliver very precise sounding capacity. IASI data assimilation has significantly improved NWP forecasts. CrIS on the NPOESS series, which will replace HIRS, is designed to enable retrievals of atmospheric temperature profiles at 1K accuracy for 1 km layers in the troposphere. The GRAS instrument on MetOp provides temperature information of high accuracy and vertical resolution in the stratosphere and upper troposphere (helping to improve analyses around the tropopause) using a GPS radio occultation (RO) technique. Its information will thus be complementary to that provided by the passive sounding instruments on MetOp. China’s FY-2 series of satellites (FY-2C, D & E), features improved measurements from October 2004 with the addition of new spectral channels to their IVISSR instrument. GPS radio occultation (RO) measurements provide high vertical resolution profiles of atmospheric refractive index that relate directly to upper air temperatures. They provide independent observations that can be utilised to calibrate all other data. Instruments are being flown on multiple low Earth orbiting satellites (such as CHAMP and SAC-C and the COSMIC constellation).

Future Satellite Observations: Systems need to be developed for real-time data exchange and use, implemented into operational meteorological data streams. Plans also need to be made to ensure future RO instruments and platforms, including on operational meteorological satellites. In response to the GCOS IP, CEOS undertook to ensure continuity of GPS RO measurements with, at a minimum, the spatial and temporal coverage established by COSMIC by 2011. CEOS will also continue efforts to exploit the complementary aspects of radiometric and geometric upper air determinations of temperature and moisture.(Source CEOS)

Satellite Missions, present and future

Data, Products, Metadata and Information Access
[ECV Matrix Main Page] [About the ECV Matrix] [Reference Documents] [Contact] [Updated May 18, 2011]

Non-Satellite or In-Situ Satellite
  • ERA-40 - ECMWF 40 Year re-analysis Data (ECMWF)This data sets contain daily and monthly analysis and forecast values interpolated to a 2.5° x 2.5° regular latitude/longitude grid. This grid is co-located with the 5° x 5° and 2.5° x 2.5° grids used for ECMWF data distribution daily on the GTS (access data) (ERA Project) (monthly mean time series) (metadata) (data documentation) (contact)
  • HadAT2 - Globally Ridded Radiodonde Temperature Anomalies from 1958 to Present (Met Office Hadley Center) is the Hadley Centre's radiosonde temperature product. This website contains a full audit trail of all the decisions made in the construction of HadAT, a range of fully gridded and globally / regionally averaged products on a monthly or seasonal resolution, and some frequently used graphics (data access) (data description) (metadata) (contact)
  • Radiosonde Innovation Composite Homogenization (RICH) Using the background forecasts as reference has the disadvantage that the forecasts themselves may be influenced by biases in the radiosonde temperatures. They may also be influenced by biases from other observing systems, most notably satellites. This problem can be avoided by creating reference series from neighboring radiosonde stations for breakpoint adjustment. This works well as long as the radiosonde network is not too sparse and as long one takes care that only homogeneous pieces of the neighboring time series are used. RICH is superficially documented in Haimberger, Tavolato and Sperka (2008), a more detailed documentation is in preparation. (gridded NetCDF formatted RICH-adjusted radiosonde data access) (metadata) (contact)

Contribution Satellite data (Source: WMO/IOC Implementation Plan for the Global Observing System for Climate in Support of the UNFCCC (2010 Update) GCOS-138/GOOS-184/GTOS-76/WMO-TD/No. 1523):

    • Microwave Sounders: (status: need to ensure continuity of MSU-like radiance bands.)
    • GNSS radio: (Status: continuity for GNSS RO contrallation needs to be secured)
    • Infrared sounders

     

  • Remote Sensing System (RSS) (NOAA/NESDIS/NCDC) Fu et al. (2004) developed a method for quantifying the stratospheric contribution to the satellite record of tropospheric temperatures and applied an adjustment to the UAH and RSS temperature record that attempts to remove the satellite contribution (cooling influence) from the middle troposphere record. This method results in trends that are larger than those from the respective source. This adjustment to both the RSS and UAH datasets is accomplished by deriving separate weighting coefficients for the MSU T2 and T4 over the tropics (30N to 30S), Northern and Southern hemispheres, and for the global mean by fitting radiosonde troposphere anomalies to radiosonde-simulated T2 and T4 anomalies over the period from 1958-2004 as T850-300 = a0 + a2*T2 + a4*T4 where T850-300 is the radiosonde 850-300 hPa layer; T2 and T4 are the radiosonde simulated MSU brightness temperature anomalies; and a0, a2, and a4 are the coefficients derived from this linear regression (Lower troposhere) (Mid-troposphere ) (Stratosphere) (data description) (contact)
  • Microwave Sounding Unit (MSU) Daily Troposphere Temperature and Precipitation Data (NOAA/ESRL/PSD) contain the Limb 93 correction and are stored in a native binary format as well as in the Hierarchical Data Format (HDF). This document also supports the Pathfinder TOVS Path C1 Daily, Pentad, and Monthly data sets stored in HDF. The NOAA satellites contributing to these data sets are, in order of their launch, TIROS-N, NOAA-6, NOAA-7, NOAA-9, NOAA-10, NOAA-11, and NOAA-12. NOAA-8 data were not used due to poor data quality. Each of the data sets have their own error characteristics, which are discussed in detail in Section 3.2.2. The dataset period of record is 1979-1994 for the temperatures, and 1979 through May 1994 for oceanic precipitation. The Daily Deep Layer data sets include daily 2.5 degree grids derived from the Microwave Sounding Units for: Lower Troposphere Temperatures (LTT), Upper Troposphere Temperatures (UTT), Lower Stratosphere Temperature (LST), Oceanic Precipitation (OP) (data access) (data documentation) (data description) (abstract) (contact)