scholarly journals HIRS channel 12 brightness temperature dataset and its correlations with major climate indices

2013 ◽  
Vol 13 (14) ◽  
pp. 6907-6920 ◽  
Author(s):  
L. Shi ◽  
C. J. Schreck III ◽  
V. O. John
Keyword(s):  
Water Vapor ◽  
Brightness Temperature ◽  
Regional Climate ◽  
Climate Indices ◽  
Teleconnection Patterns ◽  
Clear Sky ◽  
Vapor Channel ◽  
Brightness Temperatures ◽  
Spatial Coverage ◽  
The Tropics

Abstract. A new version of the High-Resolution Infrared Radiation Sounder (HIRS) upper tropospheric water vapor channel (channel 12) brightness temperature dataset is developed using intersatellite calibrated data. In this dataset, only those pixels affected by upper tropospheric clouds are discarded. Compared to the previous version that was based on column-clear-sky data, the new version has much better daily spatial coverage. The HIRS observation patterns are compared to microwave sounder measurements. The differences between the two types of sounders vary with respect to brightness temperature with larger differences for higher (dry) values. Correlations between the HIRS upper tropospheric water vapor channel brightness temperatures and several major climate indices show strong signals during cold seasons. The selected climate indices track climate variation signals covering regions from the tropics to the poles. Qualitatively, moist signals are correlated with troughs and ascending branches of the circulation, while dry signals occur with ridges and descent. These correlations show the potential of using the upper tropospheric water vapor channel brightness temperature dataset together with a suite of many atmospheric variables to monitor regional climate changes and locate global teleconnection patterns.

scholarly journals An improved HIRS upper tropospheric water vapor dataset and its correlations with major climate indices

2012 ◽  
Vol 12 (12) ◽  
pp. 33411-33442 ◽  
Author(s):  
L. Shi ◽  
C. J. Schreck III ◽  
V. O. John
Keyword(s):  
Water Vapor ◽  
Climate Changes ◽  
Regional Climate ◽  
Climate Indices ◽  
Upper Troposphere ◽  
Teleconnection Patterns ◽  
Clear Sky ◽  
Spatial Coverage ◽  
The Tropics ◽  
Atmospheric Variables

Abstract. A new version of the upper tropospheric water vapor dataset is developed using intersatellite calibrated all-sky High-Resolution Infrared Radiation Sounder (HIRS) data. In this dataset, the majority of pixels that do not affect the water vapor processing in the upper troposphere are retained. Compared to the previous version that was based on column-clear-sky data, the new version has a much better daily spatial coverage and provides a better representation of the atmosphere. The HIRS observation patterns are compared to microwave sounder measurements. The differences between the two types of sounders are examined, and the analysis displays that the differences vary with respect to brightness temperature. An examination of the correlations of the HIRS upper tropospheric water vapor with major climate indices shows that the dataset is well correlated with climate indices especially in cold seasons. The selected climate indices track climate variation signals covering regions from the tropics to the poles. The correlation analysis shows the potential of using the upper tropospheric water vapor dataset together with a suite of many atmospheric variables to monitor regional climate changes and locate global teleconnection patterns.

scholarly journals Combined SMAP–SMOS thin sea ice thickness retrieval

2019 ◽  
Vol 13 (2) ◽  
pp. 675-691 ◽  
Author(s):  
Cătălin Paţilea ◽  
Georg Heygster ◽  
Marcus Huntemann ◽  
Gunnar Spreen
Keyword(s):  
Soil Moisture ◽  
Sea Ice ◽  
Brightness Temperature ◽  
Incidence Angle ◽  
Data Availability ◽  
Ice Thickness ◽  
Polar Regions ◽  
Sea Ice Thickness ◽  
Brightness Temperatures ◽  
Spatial Coverage

Abstract. The spaceborne passive microwave sensors Soil Moisture Ocean Salinity (SMOS) and Soil Moisture Active Passive (SMAP) provide brightness temperature data in the L band (1.4 GHz). At this low frequency the atmosphere is close to transparent and in polar regions the thickness of thin sea ice can be derived. SMOS measurements cover a large incidence angle range, whereas SMAP observes at a fixed 40∘ incidence angle. By using brightness temperatures at a fixed incidence angle obtained directly (SMAP), or through interpolation (SMOS), thin sea ice thickness retrieval is more consistent as the incidence angle effects do not have to be taken into account. Here we transfer a retrieval algorithm for the thickness of thin sea ice (up to 50 cm) from SMOS data at 40 to 50∘ incidence angle to the fixed incidence angle of SMAP. The SMOS brightness temperatures (TBs) at a given incidence angle are estimated using empirical fit functions. SMAP TBs are calibrated to SMOS to provide a merged SMOS–SMAP sea ice thickness product. The new merged SMOS–SMAP thin ice thickness product was improved upon in several ways compared to previous thin ice thickness retrievals. (i) The combined product provides a better temporal and spatial coverage of the polar regions due to the usage of two sensors. (ii) The radio frequency interference (RFI) filtering method was improved, which results in higher data availability over both ocean and sea ice areas. (iii) For the intercalibration between SMOS and SMAP brightness temperatures the root mean square difference (RMSD) was reduced by 30 % relative to a prior attempt. (iv) The algorithm presented here allows also for separate retrieval from any of the two sensors, which makes the ice thickness dataset more resistant against failure of one of the sensors. A new way to estimate the uncertainty of ice thickness retrieval was implemented, which is based on the brightness temperature sensitivities.

scholarly journals Climate Model–Simulated Diurnal Cycles in HIRS Clear-Sky Brightness Temperatures

2012 ◽  
Vol 25 (17) ◽  
pp. 5845-5863 ◽  
Author(s):  
Ian A. MacKenzie ◽  
Simon F. B. Tett ◽  
Anders V. Lindfors
Keyword(s):  
Water Vapor ◽  
Brightness Temperature ◽  
Climate Models ◽  
Tropospheric Temperature ◽  
Diurnal Variability ◽  
Diurnal Cycles ◽  
Clear Sky ◽  
Recent Climate ◽  
Diurnal Behavior ◽  
Sky Brightness

Abstract Clear-sky brightness temperature measurements from the High-Resolution Infrared Radiation Sounder (HIRS) are simulated with two climate models via a radiative transfer code. The models are sampled along the HIRS orbit paths to derive diurnal climatologies of simulated brightness temperature analogous to an existing climatology based on HIRS observations. Simulated and observed climatologies are compared to assess model performance and the robustness of the observed climatology. Over land, there is good agreement between simulations and observations, with particularly high consistency for the tropospheric temperature channels. Diurnal cycles in the middle- and upper-tropospheric water vapor channels are weak in both simulations and observations, but the simulated diurnal brightness temperature ranges are smaller than are observed with different phase and there are also intermodel differences. Over sea, the absence of diurnal variability in the models’ sea surface temperatures causes an underestimate of the small diurnal cycles measured in the troposphere. The simulated and observed climatologies imply similar diurnal sampling biases in the HIRS record for the tropospheric temperature channels, but for the upper-tropospheric water vapor channel, differences in the contributions of the 24- and 12-hourly diurnal harmonics lead to differences in the implied bias. Comparison of diurnal cycles derived from HIRS-like and full model sampling suggests that the HIRS measurements are sufficient to fully constrain the diurnal behavior. Overall, the results suggest that recent climate models well represent the major processes driving the diurnal behavior of clear-sky brightness temperature in the HIRS channels. This encourages further studies of observed and simulated climate trends over the HIRS era.

scholarly journals Carbon monoxide mixing ratios over Oklahoma between 2002 and 2009 retrieved from Atmospheric Emitted Radiance Interferometer spectra

2010 ◽  
Vol 3 (5) ◽  
pp. 1319-1331 ◽  
Author(s):  
L. Yurganov ◽  
W. McMillan ◽  
C. Wilson ◽  
M. Fischer ◽  
S. Biraud ◽  
...  
Keyword(s):  
Water Vapor ◽  
Great Plains ◽  
Microwave Radiometer ◽  
Precipitable Water ◽  
Retrieval Algorithm ◽  
Southern Great Plains ◽  
Diurnal Cycles ◽  
Mixing Ratios ◽  
Clear Sky ◽  
The Tropics

Abstract. CO mixing ratios for the lowermost 2-km atmospheric layer were retrieved from downwelling infrared (IR) radiance spectra of the clear sky measured between 2002 and 2009 by a zenith-viewing Atmospheric Emitted Radiance Interferometer (AERI) deployed at the Southern Great Plains (SGP) observatory of the Atmospheric Radiation Measurements (ARM) Program near Lamont, Oklahoma. A version of a published earlier retrieval algorithm was improved and validated. Archived temperature and water vapor profiles retrieved from the same AERI spectra through automated ARM processing were used as input data for the CO retrievals. We found the archived water vapor profiles required additional constraint using SGP Microwave Radiometer retrievals of total precipitable water vapor. A correction for scattered solar light was developed as well. The retrieved CO was validated using simultaneous independently measured CO profiles from an aircraft. These tropospheric CO profiles were measured from the surface to altitudes of 4572 m a.s.l. once or twice a week between March 2006 and December 2008. The aircraft measurements were supplemented with ground-based CO measurements using a non-dispersive infrared gas correlation instrument at the SGP and retrievals from the Atmospheric IR Sounder (AIRS) above 5 km to create full tropospheric CO profiles. Comparison of the profiles convolved with averaging kernels to the AERI CO retrievals found a squared correlation coefficient of 0.57, a standard deviation of ±11.7 ppbv, a bias of -16 ppbv, and a slope of 0.92. Averaged seasonal and diurnal cycles measured by the AERI are compared with those measured continuously in situ at the SGP in the boundary layer. Monthly mean CO values measured by the AERI between 2002 and 2009 are compared with those measured by the AIRS over North America, the Northern Hemisphere mid-latitudes, and over the tropics.

scholarly journals Measuring Cloud Cover and Brightness Temperature with a Ground-Based Thermal Infrared Camera

2008 ◽  
Vol 47 (2) ◽  
pp. 683-693 ◽  
Author(s):  
Stephen Smith ◽  
Ralf Toumi
Keyword(s):  
Brightness Temperature ◽  
Cloud Cover ◽  
Infrared Camera ◽  
Thermal Infrared ◽  
Cloud Base ◽  
Clear Sky ◽  
Brightness Temperatures ◽  
External Data ◽  
Infrared Cameras ◽  
Two Parameters

Abstract Thermal infrared cameras can be used to monitor clouds and the sky at high spatial and temporal resolutions. In particular, this study shows that, without the need for any external data, cloud cover can be retrieved both day and night over a field of view extending to zenith angles of ∼80°. Zenith clear sky temperatures are estimated for cloud cover up to 80%. During periods of 50% cloud cover or more the cloud-base brightness temperatures (CBBTs) can be calculated to an accuracy of ±1 K. These calculations are made possible by using a new parameterization for the variation of sky brightness temperature with zenith angle. Both clear and cloudy conditions are found to follow this simple empirical equation more closely than the widely used parameterization of Unsworth and Monteith. A simple, angle-dependent threshold system based on cloud transmittance can then be used to retrieve cloud cover, and clear sky temperature and CBBT are calculated using the two parameters resulting from the fitting process.

scholarly journals Long term assessment of the CALIPSO Imaging Infrared Radiometer (IIR) calibration and stability through comparisons with MODIS/Aqua and SEVIRI/Meteosat

2016 ◽  
Author(s):  
Anne Garnier ◽  
Noëlle A. Scott ◽  
Jacques Pelon ◽  
Raymond Armante ◽  
Laurent Crépeau ◽  
...  
Keyword(s):  
Radiative Transfer Model ◽  
Transfer Model ◽  
Clear Sky ◽  
Brightness Temperatures ◽  
Medium Resolution ◽  
Wide Range ◽  
Air Mass Types ◽  
June July ◽  
The Tropics ◽  
Infrared Radiometer

Abstract. The quality of the calibrated radiances of the medium-resolution Imaging Infrared Radiometer (IIR) on-board the CALIPSO satellite is quantitatively controlled since the beginning of the mission in June 2006. Two complementary “relative” and “stand-alone” approaches are used, which are related to comparisons of measured brightness temperatures, and to model-to-observations comparisons, respectively. In both cases, IIR channels 1 (8.65 μm), 2 (10.6 μm), and 3 (12.05 μm) are paired with MODIS/Aqua “companion” channels 29, 31, and 32, respectively, as well as with SEVIRI/Meteosat companion channels IR8.7, IR10.8 and IR12, respectively. These pairs were selected before launch to meet radiometric, geometric and space-time constraints. The pre-launch studies were based on simulations and sensitivity studies using the 4A/OP radiative transfer model fed with the more than 2300 atmospheres of the climatological TIGR dataset further sorted out in five air mass types. Over the 9.5 years of operation since launch, in a semi-operational process, collocated measurements of IIR and of its companion channels have been compared at all latitudes over ocean, during day and night, and for all types of scenes in a wide range of brightness temperatures when dealing with the relative approach. The relative approach shows an excellent stability of IIR2-MODIS31 and IIR3-MODIS32 brightness temperature differences (BTD) since launch A slight trend of the IIR1-MODIS29 BTD, equal to −0.02 K/year on average over 9.5 years, is detected by the relative approach at all latitudes and all scene temperatures. For the stand-alone approach, clear sky measurements only are considered, which are directly compared with simulations using 4A/OP and collocated ERA-Interim reanalyses. The clear sky mask is derived from collocated observations from IIR and the CALIPSO lidar. Simulations for clear sky pixels in the tropics reproduce the differences between IIR1 and MODIS29 within 0.02 K, and between IIR2 and MODIS31 within 0.04 K, whereas IIR3-MODIS32 is larger than simulated by 0.26 K. The stand-alone approach indicates that the trend identified from the relative approach originates from MODIS29, whereas no trend (less than ±0.004 K/year) is evidenced for any of the IIR channels. Finally, a year-by-year seasonal bias between nighttime and daytime IIR-MODIS BTDs was found at mid-latitude in the northern hemisphere by the relative approach. It is due to a nighttime IIR bias as determined by the stand-alone approach, which originates from a calibration drift during day-to-night transitions. The largest bias is in June/July with IIR2 and IIR3 too warm by 0.4 K on average, and IIR1 too warm by 0.2 K.

scholarly journals Testing Climate Models Using Thermal Infrared Spectra

2008 ◽  
Vol 21 (9) ◽  
pp. 1863-1875 ◽  
Author(s):  
Stephen Leroy ◽  
James Anderson ◽  
John Dykema ◽  
Richard Goody
Keyword(s):  
Time Series ◽  
Water Vapor ◽  
Climate Models ◽  
Tropospheric Temperature ◽  
Strong Constraint ◽  
Detection Techniques ◽  
Clear Sky ◽  
Stratospheric Temperature ◽  
Occultation Data ◽  
The Tropics

Abstract An approach to test climate models with observations is presented. In this approach, it is possible to directly observe the longwave feedbacks of the climate system in time series of annual average outgoing longwave spectra. Tropospheric temperature, stratospheric temperature, water vapor, and carbon dioxide have clear and distinctive signatures in the infrared spectrum, and it is possible to detect trends of these signals unambiguously from trends in the outgoing longwave spectrum by optimal detection techniques. This approach is applied to clear-sky data in the tropics simulated from the output of an ensemble of climate models. Estimates of the water vapor–longwave feedback by this approach agree to within estimated errors with truth, and it is likely that an uncertainty of 50% can be obtained in 20 yr of a continuous time series. The correlation of tropospheric temperature and water vapor anomalies can provide a constraint on the water vapor–longwave feedback to 5% uncertainty in 20 yr, or 7% in 10 yr. Thus, it should be possible to place a strong constraint on climate models, which currently show a range of 30% in the water vapor–longwave feedback, in just 10 yr. These results may not hold in the presence of clouds, however, and so it may be necessary to supplement time series of outgoing longwave spectra with GPS radio occultation data, which are insensitive to clouds.

scholarly journals Interannual Variability of the GNSS Precipitable Water Vapor in the Global Tropics

Atmosphere ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1698
Author(s):  
Zofia Baldysz ◽  
Grzegorz Nykiel ◽  
Beata Latos ◽  
Dariusz B. Baranowski ◽  
Mariusz Figurski
Keyword(s):  
Water Vapor ◽  
Southern Oscillation ◽  
Linear Trend ◽  
Regional Climate ◽  
Singular Spectrum Analysis ◽  
Precipitable Water ◽  
Precipitable Water Vapor ◽  
Small Scale ◽  
Climate Indices ◽  
Single Station

This paper addresses the subject of inter-annual variability of the tropical precipitable water vapor (PWV) derived from 18 years of global navigation satellite system (GNSS) observations. Non-linear trends of retrieved GNSS PWV were investigated using the singular spectrum analysis (SSA) along with various climate indices. For most of the analyzed stations (~49%) the GNSS PWV anomaly was related to the El Niño Southern Oscillation (ENSO), although its influence on the PWV variability was not homogeneous. The cross-correlations coefficient values estimated between the Multivariate ENSO Index (MEI) and PWV were up to 0.78. A strong cross-correlation was also found for regional climate pattern expressed through CAR, DMI, HAW, NPGO, TNA and TSA indices. A distinct agreement was also found when instead of climate indices, the local sea surface temperature was examined (average correlation 0.60). The SSA method made it also possible to distinguish small-scale phenomena that affect PWV, such as local droughts or wetter rainy seasons. The overall nature of the investigated changes was also verified through linear trend analysis. In general, not a single station was characterized by a negative trend and its weighted mean value, calculated for all stations was equal to 0.08 ± 0.01 mm/year.

scholarly journals Thermodynamic constraint on the depth of the global tropospheric circulation

2017 ◽  
Vol 114 (31) ◽  
pp. 8181-8186 ◽  
Author(s):  
David W. J. Thompson ◽  
Sandrine Bony ◽  
Ying Li
Keyword(s):  
Water Vapor ◽  
Large Scale ◽  
Water Vapor Pressure ◽  
Static Stability ◽  
Radiative Cooling ◽  
Clear Sky ◽  
Tropospheric Circulation ◽  
Basic Physics ◽  
The Tropics ◽  
Tropopause Temperature

The troposphere is the region of the atmosphere characterized by low static stability, vigorous diabatic mixing, and widespread condensational heating in clouds. Previous research has argued that in the tropics, the upper bound on tropospheric mixing and clouds is constrained by the rapid decrease with height of the saturation water vapor pressure and hence radiative cooling by water vapor in clear-sky regions. Here the authors contend that the same basic physics play a key role in constraining the vertical structure of tropospheric mixing, tropopause temperature, and cloud-top temperature throughout the globe. It is argued that radiative cooling by water vapor plays an important role in governing the depth and amplitude of large-scale dynamics at extratropical latitudes.

scholarly journals On the Zonal Near-Constancy of Fractional Solar Absorption in the Atmosphere

2016 ◽  
Vol 29 (9) ◽  
pp. 3423-3440 ◽  
Author(s):  
Maria Z. Hakuba ◽  
Doris Folini ◽  
Martin Wild
Keyword(s):  
Water Vapor ◽  
Global Scale ◽  
Solar Absorption ◽  
Clear Sky ◽  
Latitude Dependence ◽  
Zero Effect ◽  
Aerosol Effects ◽  
The Tropics ◽  
Water Vapor Path ◽  
Sky Conditions

Abstract Over Europe, a recent study found the fractional all-sky atmospheric solar absorption to be largely unaffected by variations in latitude, remaining nearly constant at its regional mean of 23% ± 1%, relative to the respective top-of-atmosphere insolation. The satellite-based CERES EBAF dataset (2000–10) confirms the weak latitude dependence within 23% ± 2%, representative of the near-global scale between 60°S and 60°N. Under clear-sky conditions, the fractional absorption follows the spatial imprint of the water vapor path, peaking in the tropics and decreasing toward the poles, accompanied by a slight hemispheric asymmetry. In the northern extratropics, the clear-sky absorption attains zonal near-constancy due to combined water vapor, surface albedo, and aerosol effects that are largely amiss in the Southern Hemisphere. In line with earlier studies, the CERES EBAF suggests an increase in atmospheric solar absorption due to clouds by on average 1.5% (5 W m−2) from 21.5% (78 W m−2) under clear-sky conditions to 23% (83 W m−2) under all-sky conditions (60°S–60°N). The low-level clouds in the extratropics act to enhance the absorption, whereas the high clouds in the tropics exhibit a near-zero effect. Consequently, clouds reduce the latitude dependence of fractional atmospheric solar absorption and yield a near-constant zonal mean pattern under all-sky conditions. In the GEWEX-SRB satellite product and the historical simulations from phase 5 of CMIP (CMIP5; 1996–2005, multimodel mean) the amount of insolation absorbed by the atmosphere is reduced by around −1.3% (5 W m−2) with respect to the CERES EBAF mean. The zonal variability and magnitude of the atmospheric cloud effect are, however, largely in line.

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