Remote Sensing of the Thermodynamic State of the Atmospheric Boundary Layer by Ground-Based Microwave Radiometry

Güldner, J.; Spänkuch, D.

doi:10.1175/1520-0426(2001)018<0925:rsotts>2.0.co;2

Cited by 122 publications

(114 citation statements)

References 30 publications

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“…Studies evaluating the accuracy of MWR measurements using radiosonde observations show consistent results with differences of 1-2 K in temperature, < 0.4 g m −3 in water vapor density, and < 20 % in humidity for most weather conditions (Güldner and Spänkuch, 2001;Liljegren et al, 2001;Ware et al, 2003;Crewell and Löhnert, 2007;Cimini et al, 2011;Löhnert and Maier, 2012). Similar results were derived from comparisons between MWR and in situ tower observations with differences in temperature ranging from 0.7-1.7 K (Crewell and Löhnert, 2007;Friedrich et al, 2012).…”

Section: Introductionsupporting

confidence: 60%

“…Several studies have focused on evaluating the accuracy of temperature, water vapor density, and humidity retrieved by MWRs (e.g., Güldner and Spänkuch, 2001;Liljegren et al, 2001;Ware et al, 2003;Crewell and Löhnert, 2007;Cimini et al, 2011;Friedrich et al, 2012;Löhnert and Maier, 2012) and virtual temperature (T v ) retrieved by WPRs with RASS (May et al, 1989;Moran and Strauch, 1994;Angevine et al, 1998;Görsdorf and Lehmann, 2000). Studies evaluating the accuracy of MWR measurements using radiosonde observations show consistent results with differences of 1-2 K in temperature, < 0.4 g m −3 in water vapor density, and < 20 % in humidity for most weather conditions (Güldner and Spänkuch, 2001;Liljegren et al, 2001;Ware et al, 2003;Crewell and Löhnert, 2007;Cimini et al, 2011;Löhnert and Maier, 2012).…”

Section: Introductionmentioning

confidence: 99%

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Assessing the accuracy of microwave radiometers and radio acoustic sounding systems for wind energy applications

et al. 2017

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Abstract. To assess current remote-sensing capabilities for wind energy applications, a remote-sensing system evaluation study, called XPIA (eXperimental Planetary boundary layer Instrument Assessment), was held in the spring of 2015 at NOAA's Boulder Atmospheric Observatory (BAO) facility. Several remote-sensing platforms were evaluated to determine their suitability for the verification and validation processes used to test the accuracy of numerical weather prediction models.The evaluation of these platforms was performed with respect to well-defined reference systems: the BAO's 300 m tower equipped at six levels (50, 100, 150, 200, 250, and 300 m) with 12 sonic anemometers and six temperature (T ) and relative humidity (RH) sensors; and approximately 60 radiosonde launches.In this study we first employ these reference measurements to validate temperature profiles retrieved by two co-located microwave radiometers (MWRs) as well as virtual temperature (T v ) measured by co-located wind profiling radars equipped with radio acoustic sounding systems (RASSs). Results indicate a mean absolute error (MAE) in the temperature retrieved by the microwave radiometers below 1.5 K in the lowest 5 km of the atmosphere and a mean absolute error in the virtual temperature measured by the radio acoustic sounding systems below 0.8 K in the layer of the atmosphere covered by these measurements (up to approximately 1.6-2 km). We also investigated the benefit of the vertical velocity correction applied to the speed of sound before computing the virtual temperature by the radio acoustic sounding systems. We find that using this correction frequently increases the RASS error, and that it should not be routinely applied to all data.Water vapor density (WVD) profiles measured by the MWRs were also compared with similar measurements from the soundings, showing the capability of MWRs to follow the vertical profile measured by the sounding and finding a mean absolute error below 0.5 g m −3 in the lowest 5 km of the atmosphere. However, the relative humidity profiles measured by the microwave radiometer lack the high-resolution details available from radiosonde profiles. An encouraging and significant finding of this study was that the coefficient of determination between the lapse rate measured by the microwave radiometer and the tower measurements over the tower levels between 50 and 300 m ranged from 0.76 to 0.91, proving that these remote-sensing instruments can provide accurate information on atmospheric stability conditions in the lower boundary layer.

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Section: Introductionsupporting

confidence: 60%

Section: Introductionmentioning

confidence: 99%

Assessing the accuracy of microwave radiometers and radio acoustic sounding systems for wind energy applications

et al. 2017

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“…Similar discrepancies in the temperature were found in other studies where colocated radiosondes and microwave radiometers were compared. Güldner and Spänkuch (2001) reported differences of 0.7 K in the planetary boundary layer and 1.6 K at 7 km while Löhnert and Maier (2012) found discrepancies of 0.5 K in the lower boundary layer that increased to 1.7 K at 4 km height. In order to better understand the cloud effect on the temperature retrievals we have classified the different cloud cases according to the amount of liquid water.…”

Section: Statistical Study Of Temperature Profilesmentioning

confidence: 99%

An integrated approach toward the incorporation of clouds in the temperature retrievals from microwave measurements

2014

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Abstract. In this paper, we address the characterization of clouds and its inclusion in microwave retrievals in order to study its effect on tropospheric temperature profiles measured by TEMPERA radiometer. TEMPERA is the first ground-based microwave radiometer that makes it possible to obtain temperature profiles in the troposphere and stratosphere at the same time. In order to characterize the clouds a multi-instrumental approach has been adopted. Cloud base altitudes were detected using ceilometer measurements while the integrated liquid water was measured by TROWARA radiometer. Both instruments are co-located with TEMPERA in Bern (Switzerland). Using this information and a constant Liquid Water Content value inside the cloud a liquid profile is provided to characterize the clouds in the inversion algorithm. Microwave temperature profiles have been obtained incorporating this water liquid profile in the inversion algorithm and also without considering the clouds, in order to assess its effect on the retrievals. The results have been compared with the temperature profiles from radiosondes which are launched twice a day at the aerological station of MeteoSwiss in Payerne (40 km W of Bern). Almost 1 year of data have been analysed and 60 non-precipitating cloud cases were studied. The statistical analysis carried out over all the cases evidenced that temperature retrievals improved in most of the cases when clouds were incorporated in the inversion algorithm.

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“…This study uses observations from the Radiometrics TP/WVP-3000 microwave radiometer (Güldner and Spankuch, 2001), but with a rapid observing cycle to allow the passage of cloud to be resolved for the first time with this type of radiometer in the UK. The radiometer viewed in the zenith direction with very high time resolution (∼12 s).…”

Section: Instrumentationmentioning

confidence: 99%

High time resolution boundary layer description using combined remote sensing instruments

et al. 2008

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Abstract. Ground based remote sensing systems for future observation operations will allow continuous monitoring of the lower troposphere at temporal resolutions much better than every 30 min. Observations which may be considered spurious from an individual instrument can be validated or eliminated when considered in conjunction with measurements from other instruments observing at the same location. Thus, improved quality control of atmospheric profiles from microwave radiometers and wind profilers should be sought by considering the measurements from different systems together rather than individually. In future test bed deployments for future operational observing systems, this should be aided by observations from laser ceilometers and cloud radars. Observations of changes in atmospheric profiles at high temporal resolution in the lower troposphere are presented from a 12 channel microwave radiometer and 1290 MHz UHF wind profiler deployed in southern England during the CSIP field experiment in July/August 2005. The observations chosen were from days when thunderstorms occurred in southern England. Rapid changes near the surface in dry layers are considered, both when rain/hail may be falling from above and where the dry air is associated with cold pools behind organised thunderstorms. Also, short term variations in atmospheric profiles and vertical stability are presented on a day with occasional low cloud, when thunderstorms triggered 50 km down wind of the observing site Improved quality control of the individual remote sensing systems need to be implemented, examining the basic quality of the underlying observations as well as the final outputs, and so for instance eliminating ground clutter as far as possible from the basic Doppler spectra measurements of the wind profiler. In this study, this was performed manually. The potential of incorporating these types of instruments in future upper air observational networks leads to the challenge Correspondence to: C. Gaffard (catherine.gaffard@metoffice.gov.uk) to improve the observing systems and also to exploit measurements at high temporal resolution in numerical weather prediction. These examples are intended to inform potential operational users of the changes in atmospheric structure that can be observed with the new types of observing system.

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Remote Sensing of the Thermodynamic State of the Atmospheric Boundary Layer by Ground-Based Microwave Radiometry

Cited by 122 publications

References 30 publications

Assessing the accuracy of microwave radiometers and radio acoustic sounding systems for wind energy applications

Assessing the accuracy of microwave radiometers and radio acoustic sounding systems for wind energy applications

An integrated approach toward the incorporation of clouds in the temperature retrievals from microwave measurements

High time resolution boundary layer description using combined remote sensing instruments

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