UAH satellite temperature dataset

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The UAH satellite temperature dataset, developed at the University of Alabama in Huntsville, infers the temperature of various atmospheric layers from satellite measurements of the oxygen radiance in the microwave band, using Microwave Sounding Unit temperature measurements.

Contents

It was the first global temperature datasets developed from satellite information and has been used as a tool for research into surface and atmospheric temperature changes. The dataset is published by John Christy et al. and formerly jointly with Roy Spencer.

Satellite temperature measurements

Satellites do not measure temperature directly. They measure radiances in various wavelength bands, from which temperature may be inferred. [1] [2] The resulting temperature profiles depend on details of the methods that are used to obtain temperatures from radiances. As a result, different groups that have analyzed the satellite data have obtained different temperature data (see Microwave Sounding Unit temperature measurements). Among these groups are Remote Sensing Systems (RSS) and the University of Alabama in Huntsville (UAH). The satellite series is not fully homogeneous - it is constructed from a series of satellites starting with the 1978 TIROS-N, where different satellites had similar but not identical instrumentation. The sensors deteriorate over time, and corrections are necessary for satellite drift and orbital decay. Particularly large differences between reconstructed temperature series occur at the few times when there is little temporal overlap between successive satellites, making intercalibration difficult.

Description of the data

The UAH dataset is produced by one of the groups reconstructing temperature from radiance.

UAH provide data on three broad levels of the atmosphere.

Data are provided as temperature anomalies against the seasonal average over a past basis period, as well as in absolute temperature values. The baseline period for the published temperature anomalies was changed in January 2021 from 1981-2010 to 1991-2020. [4]

All the data products can be downloaded from the UAH server. [5]

Recent trend summary

To compare to the trend from the surface temperature record (+0.161±0.033 °C/decade from 1979 to 2012 according to NASA GISS [6] ) it is most appropriate to derive trends for the part of the atmosphere nearest the surface, i.e., the lower troposphere. Doing this, through December 2019, the UAH linear temperature trend 1979-2019 shows a warming of +0.13 °C/decade. [7] [8]

For comparison, a different group, Remote Sensing Systems (RSS), also analyzes the MSU data. From their data: the RSS linear temperature trend shows a warming of +0.208 °C/decade. [9] [10]

Geographic coverage

Data are available as global, hemispheric, zonal, and gridded averages. The global average covers 97-98% of Earth's surface, excluding only latitudes above +85 degrees, below -85 degrees and, in the cases of TLT and TMT, some areas with land above 1500 m altitude. The hemispheric averages are over the northern and southern hemispheres 0 to +/-85 degrees. The gridded data provide an almost global temperature map. [3] However, other sources state that the globally averaged trends are computed over latitudes from 82.5S to 82.5N (70S to 82.5N for channel TLT). [11]

Temporal coverage

Daily global, hemispheric and zonal data are available. Monthly averages are available in gridded format as well as by hemisphere and globally.

Each set has data back to December 1978.

Comparison with other data and models

In comparing these measurements to surface temperature models, it is important to note that values for the lower troposphere measurements taken by the MSU are a weighted average of temperatures over multiple altitudes (roughly 0 to 12 km), and not a surface temperature (see figure in Microwave Sounding Unit temperature measurements article). The results are thus not precisely comparable to surface temperature records or models.

Pre-1998 results published by UAH showed no warming of the atmosphere. In a 1998 paper, Wentz and Schabel showed this (along with other discrepancies) was due to the orbital decay of the NOAA satellites. [12] With these errors corrected, the UAH data showed a 0.07 °C/decade increase in lower troposphere temperature.

Some discrepancies between the UAH temperature measurements and temperatures measured by other groups remain, with (as of 2019) the lower troposphere temperature trend from 1979-2019 calculated as +0.13 °C/decade by UAH, [7] [8] and calculated at +0.208 °C/decade by RSS. [9] [10]

A more detailed discussion can be found in the Comparison with surface trends section of the Microwave Sounding Unit temperature measurements article.

Corrections made

The table below summarizes the adjustments that have been applied to the UAH TLT dataset. [13] [14] The 'trend correction' refers to the change in global mean decadal temperature trend in degrees Celsius/decade as a result of the correction.

UAH versionMain adjustmentTrend correctionYear
ASimple bias correction1992
BLinear diurnal drift correction-0.031994
CRemoval of residual
annual cycle related to
hot target variation		0.031997
DOrbital decay0.101998
DRemoval of dependence
of time variations of
hot target temperature		-0.071998
5.0Non-linear diurnal correction0.0082003
5.1Tightened criteria for data acceptance-0.0042004
5.2Correction of diurnal drift adjustment0.0352005
5.3Annual cycle correction02009
5.4New annual cycle02010
6.0 betaExtensive revision-0.026 [15] 2015

NOAA-11 played a significant role in a 2005 study by Mears et al. identifying an error in the diurnal correction that leads to the 40% jump in Spencer and Christy's trend from version 5.1 to 5.2. [16]

Christy et al. asserted in a 2007 paper that the tropical temperature trends from radiosondes matches more closely with their v5.2 UAH-TLT dataset than with RSS v2.1. [17]

Much of the difference, at least in the Lower troposphere global average decadal trend between UAH and RSS, had been removed with the release of RSS version 3.3 in January 2011, at which time the RSS and UAH TLT were now within 0.003 K/decade of one another. Significant differences remained, however, in the Mid Troposphere (TMT) decadal trends. However, in June 2017 RSS released version 4 which significantly increased the trend from 0.136 to 0.184 K/decade substantially increasing the difference again.

A beta version of 6.0 of the dataset was released on April 28, 2015 via blog post. [15] This dataset has higher spatial resolution and uses new methods for gridpoint averaging.

Related Research Articles

<span class="mw-page-title-main">Satellite temperature measurement</span> Measurements of atmospheric, land surface or sea temperature by satellites.

Satellite temperature measurements are inferences of the temperature of the atmosphere at various altitudes as well as sea and land surface temperatures obtained from radiometric measurements by satellites. These measurements can be used to locate weather fronts, monitor the El Niño-Southern Oscillation, determine the strength of tropical cyclones, study urban heat islands and monitor the global climate. Wildfires, volcanos, and industrial hot spots can also be found via thermal imaging from weather satellites.

<span class="mw-page-title-main">Tropopause</span> The boundary of the atmosphere between the troposphere and stratosphere

The tropopause is the atmospheric boundary that demarcates the troposphere from the stratosphere, which are the lowest two of the five layers of the atmosphere of Earth. The tropopause is a thermodynamic gradient-stratification layer that marks the end of the troposphere, and is approximately 17 kilometres (11 mi) above the equatorial regions, and approximately 9 kilometres (5.6 mi) above the polar regions.

<span class="mw-page-title-main">Instrumental temperature record</span> In situ measurements that provide the temperature of Earths climate system

The instrumental temperature record is a record of temperatures within Earth's climate based on direct measurement of air temperature and ocean temperature. Instrumental temperature records do not use indirect reconstructions using climate proxy data such as from tree rings and marine sediments. Instead, data is collected from thousands of meteorological stations, buoys and ships around the globe. Areas that are densely populated tend have a high density of measurements points. In contrast, temperature observations are more spread out in sparsely populated areas such as polar regions and deserts, as well as in many regions of Africa and South America. In the past, thermometers were read manually to record temperatures. Nowadays, measurements are usually connected with electronic sensors which transmit data automatically. Surface temperature data is usually presented as anomalies rather than as absolute values. A temperature anomaly is presented compared to a reference value, also called baseline period or long-term average). For example, a commonly used baseline period is the time period from 1951 to 1980.

<span class="mw-page-title-main">Microwave radiometer</span> Tool measuring EM radiation at 0.3–300-GHz frequency

A microwave radiometer (MWR) is a radiometer that measures energy emitted at one millimeter-to-metre wavelengths (frequencies of 0.3–300 GHz) known as microwaves. Microwave radiometers are very sensitive receivers designed to measure thermally-emitted electromagnetic radiation. They are usually equipped with multiple receiving channels to derive the characteristic emission spectrum of planetary atmospheres, surfaces or extraterrestrial objects. Microwave radiometers are utilized in a variety of environmental and engineering applications, including remote sensing, weather forecasting, climate monitoring, radio astronomy and radio propagation studies.

<span class="mw-page-title-main">Roy Spencer (meteorologist)</span>

Roy Warren Spencer is an American meteorologist. He is a principal research scientist at the University of Alabama in Huntsville, and the U.S. Science Team leader for the Advanced Microwave Scanning Radiometer (AMSR-E) on NASA's Aqua satellite. He has served as senior scientist for climate studies at NASA's Marshall Space Flight Center. He is known for his satellite-based temperature monitoring work, for which he was awarded the American Meteorological Society's Special Award. Spencer disagrees with the scientific consensus that most global warming in the past 50 years is the result of human activity, instead believing that anthropogenic greenhouse gas emissions have caused some warming, but that influence is small compared to natural variations in global average cloud cover.

<span class="mw-page-title-main">MOPITT</span> Canadian scientific instrument aboard NASAs Terra satellite

MOPITT is an ongoing astronomical instrument aboard NASA's Terra satellite that measures global tropospheric carbon monoxide levels. It is part of NASA's Earth Observing System (EOS), and combined with the other payload remote sensors on the Terra satellite, the spacecraft monitors the Earth's environment and climate changes. Following its construction in Canada, MOPITT was launched into Earth's orbit in 1999 and utilizes gas correlation spectroscopy to measure the presence of different gases in the troposphere. The fundamental operations occur in its optical system composed of two optical tables holding the bulk of the apparatus. Results from the MOPITT enable scientists to better understand carbon monoxide's effects on a global scale, and various studies have been conducted based on MOPITT's measurements.

<span class="mw-page-title-main">EUMETSAT</span> European intergovernmental organisation

The European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) is an intergovernmental organisation created through an international convention agreed by a current total of 30 European Member States.

John Raymond Christy is a climate scientist at the University of Alabama in Huntsville (UAH) whose chief interests are satellite remote sensing of global climate and global climate change. He is best known, jointly with Roy Spencer, for the first successful development of a satellite temperature record.

<span class="mw-page-title-main">Sea surface temperature</span> Water temperature close to the oceans surface

Sea surface temperature (SST), or ocean surface temperature, is the ocean temperature close to the surface. The exact meaning of surface varies in the literature and in practice. It is usually between 1 millimetre (0.04 in) and 20 metres (70 ft) below the sea surface. Sea surface temperatures greatly modify air masses in the Earth's atmosphere within a short distance of the shore. Local areas of heavy snow can form in bands downwind of warm water bodies within an otherwise cold air mass. Warm sea surface temperatures can develop and strengthen cyclones over the ocean. Tropical cyclones can also cause a cool wake. This is due to turbulent mixing of the upper 30 metres (100 ft) of the ocean. Sea surface temperature changes during the day. This is like the air above it, but to a lesser degree. There is less variation in sea surface temperature on breezy days than on calm days. The thermohaline circulation has a major impact on average sea surface temperature throughout most of the world's oceans.

<span class="mw-page-title-main">Global temperature record</span> Fluctuations of the Earths temperature over time

The global temperature record shows the fluctuations of the temperature of the atmosphere and the oceans through various spans of time. There are numerous estimates of temperatures since the end of the Pleistocene glaciation, particularly during the current Holocene epoch. Some temperature information is available through geologic evidence, going back millions of years. More recently, information from ice cores covers the period from 800,000 years before the present time until now. A study of the paleoclimate covers the time period from 12,000 years ago to the present. Tree rings and measurements from ice cores can give evidence about the global temperature from 1,000-2,000 years before the present until now. The most detailed information exists since 1850, when methodical thermometer-based records began. Modifications on the Stevenson-type screen were made for uniform instrument measurements around 1880.

<span class="mw-page-title-main">Temperature measurement</span> Recording of temperature

Temperature measurement describes the process of measuring a current temperature for immediate or later evaluation. Datasets consisting of repeated standardized measurements can be used to assess temperature trends.

<span class="mw-page-title-main">Megha-Tropiques</span> Deorbited Indo-French weather satellite

Megha-Tropiques was a satellite mission to study the water cycle in the tropical atmosphere in the context of climate change. A collaborative effort between Indian Space Research Organisation (ISRO) and French Centre National d’Etudes Spatiales (CNES), Megha-Tropiques was successfully deployed into orbit by a PSLV rocket in October 2011.

Remote Sensing Systems (RSS) is a private research company founded in 1974 by Frank Wentz. It processes microwave data from a variety of NASA satellites. Most of their research is supported by the Earth Science Enterprise program. The company is based in Santa Rosa, California.

Carl Mears is a Senior Scientist, at Remote Sensing Systems, since 1998. He has worked on validation of SSM/I derived winds, and rain-flagging algorithm for the QuikScat scatterometer. He is best known for his work with Frank Wentz in developing a satellite temperature record from MSU and AMSU. Intercomparison of this record with the earlier UAH satellite temperature record, developed by John Christy and Roy Spencer, revealed deficiencies in the earlier work; specifically, the warming trend in the RSS version is larger than the UAH one.

The microwave sounding unit (MSU) was the predecessor to the Advanced Microwave Sounding Unit (AMSU).

Frank Wentz is the CEO and director of Remote Sensing Systems, a company he founded in 1974, which specializes in satellite microwave remote sensing research. Together with Carl Mears, he is best known for developing a satellite temperature record from MSU and AMSU. Intercomparison of this record with the earlier UAH satellite temperature record, developed by John Christy and Roy Spencer, revealed deficiencies in the earlier work; specifically, the warming trend in the RSS version is larger than the University of Alabama in Huntsville (UAH) one. From 1978 to 1982, Wentz was a member of NASA's SeaSat Experiment Team involved in the development of physically based retrieval methods for microwave scatterometers and radiometers. He has also investigated the effect of climate change on satellite-derived evaporation, precipitation and surface wind values. His findings are different from most climate change model predictions.

<span class="mw-page-title-main">Microwave Sounding Unit temperature measurements</span>

Microwave Sounding Unit temperature measurements refers to temperature measurement using the Microwave Sounding Unit instrument and is one of several methods of measuring Earth atmospheric temperature from satellites. Microwave measurements have been obtained from the troposphere since 1979, when they were included within NOAA weather satellites, starting with TIROS-N. By comparison, the usable balloon (radiosonde) record begins in 1958 but has less geographic coverage and is less uniform.

<span class="mw-page-title-main">Temperature anomaly</span>

Temperature anomaly is the difference, positive or negative, of a temperature from a base or reference value, normally chosen as an average of temperatures over a certain reference or base period. In atmospheric sciences, the average temperature is commonly calculated over a period of at least 30 years over a homogeneous geographic region, or globally over the entire planet.

<span class="mw-page-title-main">Global warming hiatus</span> Period of little Earth temperature change

A global warming hiatus, also sometimes referred to as a global warming pause or a global warming slowdown, is a period of relatively little change in globally averaged surface temperatures. In the current episode of global warming many such 15-year periods appear in the surface temperature record, along with robust evidence of the long-term warming trend. Such a "hiatus" is shorter than the 30-year periods that climate is classically averaged over.

Atmospheric correction for Interferometric Synthetic ApertureRadar (InSAR) technique is a set of different methods to remove artefact displacement from an interferogram caused by the effect of weather variables such as humidity, temperature, and pressure. An interferogram is generated by processing two synthetic-aperture radar images before and after a geophysical event like an earthquake. Corrections for atmospheric variations are an important stage of InSAR data processing in many study areas to measure surface displacement because relative humidity differences of 20% can cause inaccuracies of 10–14 cm InSAR due to varying delays in the radar signal. Overall, atmospheric correction methods can be divided into two categories: a) Using Atmospheric Phase Screen (APS) statistical properties and b) Using auxiliary (external) data such as GPS measurements, multi-spectral observations, local meteorological models, and global atmospheric models.

References

  1. ↑ National Research Council (U.S.). Committee on Earth Studies (2000). "Atmospheric Soundings". Issues in the Integration of Research and Operational Satellite Systems for Climate Research: Part I. Science and Design. Washington, D.C.: National Academy Press. pp. 17–24. ISBN   0-309-51527-0.
  2. ↑ Uddstrom, Michael J. (1988). "Retrieval of Atmospheric Profiles from Satellite Radiance Data by Typical Shape Function Maximum a Posteriori Simultaneous Retrieval Estimators". Journal of Applied Meteorology. 27 (5): 515–549. Bibcode:1988JApMe..27..515U. doi: 10.1175/1520-0450(1988)027<0515:ROAPFS>2.0.CO;2 .
  3. 1 2 "INFORMATION CONCERNING THE MSU DATA FILES" . Retrieved February 28, 2011.
  4. ↑ Dr Roy Spencer. "UAH Global Temperature Update for January 2021: +0.12 deg. C (new base period)".
  5. ↑ "UAH MSU Data".
  6. ↑ "IPCC AR5 WG1 Chapter 2: Observations Atmosphere and Surface" (PDF). ipcc.ch. Intergovernmental Panel on Climate Change. 2013. p. 193. Retrieved February 3, 2017.
  7. 1 2 Spencer, Roy W. (January 3, 2020). "UAH Global Temperature Update for December 2019: +0.56 deg. C". www.drroyspencer.com. Retrieved January 11, 2017.
  8. 1 2 "UAH v6.0 TLT" (trend data at bottom of file). nsstc.uah.edu. The National Space Science & Technology Center. Retrieved February 3, 2017.
  9. 1 2 Remote Sensing Services, Earth Microwave Data Center, MSU & AMSU Time Series Trend Browse Tool. Retrieved 15 Jan. 2020.
  10. 1 2 "Upper Air Temperature: Decadal Trends". remss.com. Remote Sensing Systems . Retrieved February 3, 2017.
  11. ↑ "Upper Air Temperature". remss.com. Remote Sensing Systems. 2024. Retrieved June 4, 2024.
  12. ↑ "Archived copy" (PDF). Archived from the original (PDF) on January 15, 2010. Retrieved January 7, 2014.{{cite web}}: CS1 maint: archived copy as title (link)
  13. ↑ "UAH adjustment" . Retrieved January 15, 2011.[ permanent dead link ]
  14. ↑ "CCSP sap 1.1" (PDF). Archived from the original (PDF) on December 24, 2010. Retrieved January 15, 2011.
  15. 1 2 "Version 6.0 of the UAH Temperature Dataset Released: New LT Trend = +0.11 C/decade" . Retrieved January 11, 2017.
  16. ↑ Mears, Carl A.; Wentz, Frank J. (2005). "The Effect of Diurnal Correction on Satellite-Derived Lower Tropospheric Temperature". Science. 309 (5740): 1548–1551. Bibcode:2005Sci...309.1548M. doi: 10.1126/science.1114772 . PMID   16141071. S2CID   17118845.
  17. ↑ Christy, J. R.; Norris, W. B.; Spencer, R. W.; Hnilo, J. J. (2007). "Tropospheric temperature change since 1979 from tropical radiosonde and satellite measurements". Journal of Geophysical Research. 112 (D6): D06102. Bibcode:2007JGRD..112.6102C. doi: 10.1029/2005JD006881 .

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