Vaisala Oy

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Trends

Author Order

Document Type

Co-Authors

Larry M. Miloshevich

NSF National Center for Atmospheric Research

A. Paukkunen

Vaisala (Finland)

Holger Vömel

NSF National Center for Atmospheric Research

Andrew J. Heymsfield

NSF National Center for Atmospheric Research

S. J. Oltmans

National Oceanic and Atmospheric Administration

Jan Lönnqvist

Vaisala (Finland)

Cooperative Institutions

NSF National Center for Atmospheric Research

University of Colorado Boulder

Cooperative Institute for Research in Environmental Sciences

U.S. National Science Foundation

German Meteorological Service

University Corporation for Atmospheric Research

NOAA Earth System Research Laboratory

National Oceanic and Atmospheric Administration

Vaisala (Finland)

Earth Observing Laboratory

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Field

Improved Water Vapor Measurements from ARM Radiosondes

Larry M. Miloshevich Andrew J. Heymsfield A. Paukkunen Vaisala Oy

Accurate radiosonde measurements of water vapor in the mid and upper troposphere are important for such applications as evaluating remote-sensor water vapor retrievals, initializing numerical models, and improving parameterizations of radiative and cloud processes. Measurements of relative humidity (RH) from Vaisala radiosondes are subject to several measurement errors, most of which increase in magnitude with decreasing temperature (Miloshevich et al. 2000). Several of these measurement errors have already been corrected in part of the Atmospheric Radiation Measurement (ARM) Program dataset by Barry Lesht and others. This research program addresses two remaining measurement errors that can be substantial in the mid and especially upper troposphere (UT).

Initialization

Source

Cite

Citations (1)

Application of backscatter lidar to airport traffic safety

Conference on Lasers and Electro-Optics Europe (1994)

Jan Lönnqvist Vaisala Oy

A well established commercial application for lidar technology is cloud base height and vertical visibility measurement for airport and aviation safety purposes: Most major airports today are equipped with laser ceilometers , which are actually small, relatively low-cost, eye safe backscatter lidars. 1

Visibility

Backscatter (email)

10.1364/cleo_europe.1994.cfd5

Cite

Citations (0)

Preliminary Correction of Vaisala Radiosonde Humidity Measurements for Slow Sensor Time-Response at Cold Temperatures

Larry M. Miloshevich Andrew J. Heymsfield A. Paukkunen Vaisala Oy

The goal of this study is to improve the accuracy of relative humidity (RH) measurements from Vaisala radiosondes, especially in the upper troposphere (UT), by correcting measurement error that results from slow time-response of the RH sensor at cold temperatures. Accurate water vapor profiles are important for such applications as input to radiative transfer algorithms, calibration, or evaluation of remote-sensor water vapor retrievals, initializing numerical models, and improving parameterizations of cloud processes. Inaccurate measurement of water vapor profiles has been shown by Atmospheric Radiation Measurement (ARM) Program studies to be the primary limitation to improving clear-sky radiative transfer models (e.g., Clough et al. 1999). Although water vapor concentrations are much less in the UT than at lower levels, atmospheric cooling rates in the UT due to water vapor exceed those in the mid troposphere due to the very strong contribution by the wave number range 250 cm to 350 cm (Clough et al. 1992). RH measurements from Vaisala RS80-H radiosondes are heavily relied upon by ARM to characterize the water vapor profile in the UT, because other means such as Raman Lidar or Differential Absorption Lidar have accuracy and/or vertical resolution limitations in the UT (see Turner et al. 2000).

Source

Cite

Citations (4)

Impact of Vaisala Radiosonde Humidity Corrections on ARM IOP Data

Larry M. Miloshevich A. Paukkunen Vaisala Oy Holger Vömel S. J. Oltmans

Radiosonde humidity measurements are fundamentally important to a variety of applications, including radiative transfer calculations, validation of remote-sensor retrievals, parameterization of cloud processes, and initialization of (or assimilation into) numerical models. Vaisala radiosondes, used by the Atmospheric Radiation Measurement (ARM) Program and extensively throughout the world, are known to have accuracy limitations that result from several identified sources of measurement error (Miloshevich et al. 2001a). A systematic dry bias in Vaisala radiosonde humidity measurements has been noted in comparison to satellite water vapor retrievals (Soden and Lanzante 1996) and Raman lidar measurements (Ferrare et al. 1995), and in underpredicting clouds and precipitation in a numerical weather prediction model (Lorenc et al. 1996). The concurrent observations that variability exists in the accuracy of the ARM radiosonde humidity measurements when radiosondes from different calibration batches are used (Lesht 1999), and that unrealistically dry tropical boundary layers were frequently observed in the radiosonde data during the Tropical Ocean Global Atmosphere-Coupled Ocean Atmosphere Response Experiment (TOGA-COARE) (Zipser and Johnson 1998), led to a substantial effort by Vaisala and the National Center for Atmospheric Research (NCAR) to identify the sources of the measurement inaccuracy and develop corrections (Wang et al. 2002).

Dropsonde

Atmospheric Infrared Sounder

Source

Cite

Citations (6)

In Situ Validation of a Correction for Time-Lag and Bias Errors in Vaisala RS80-H Radiosonde Humidity Measurements

Larry M. Miloshevich Holger Vömel S. J. Oltmans A. Paukkunen Vaisala Oy

Radiosonde relative humidity (RH) measurements are fundamentally important to Atmospheric Radiation Measurement (ARM) Program goals because they are used in a wide variety of both operational and research applications, including initialization of numerical models and evaluation of model results, validation of remote-sensor water vapor retrievals, construction of water vapor climatologies and studies of climate trends, parameterization of cloud processes, and as input to radiative transfer calculations. A systematic dry bias in Vaisala radiosonde humidity measurements has been noted in comparison to Raman lidar measurements (Ferrare et al. 1995) and satellite water vapor retrievals (Soden and Lanzante 1996), and in underpredicting clouds and precipitation in a numerical weather prediction model (Lorenc et al. 1996). Direct observations of bias error in Vaisala radiosonde humidity measurements have also been reported: dual-radiosonde launches at the Oklahoma ARM site showed offsets between radiosondes from different calibration batches that measured the same air (Lesht 1998); unrealistically dry tropical boundary layers were frequently observed during the Tropical Ocean Global Atmosphere-Coupled Ocean Atmosphere Response (TOGA-COARE) experiment (Zipser and Johnson 1998); and humidities far below ice-saturation were measured in cirrus clouds when simultaneous measurements of detailed ice crystal characteristics indicated that the crystals were pristine and therefore actively growing in an ice-supersaturated environment (Miloshevich et al. 2001a).

Cirrus

Source

Cite

Citations (12)

Pressure influence in capacitive humidity measurement

Vaisala Oy

We investigated the behaviour of a capacitive humidity transducer (Vaisala HMP 234) upon pressure exposure of nitrogen and helium up to 100 bar, using a humidity generator based on saturation of the gases at temperatures below ambient. The increased saturated vapour pressure of water in the presence of nitrogen and helium (enhancement effect) was quantitatively taken into account. The sensor output was found to decrease with nitrogen pressure at fixed relative humidity (RH). Still, by taking the total pressure as an independent calibration parameter, the device can be used in nitrogen gas within error bounds of 9 1% RH. For helium no deviation of the sensor output with pressure was observed, showing that the deviation strongly depends on gas properties. For similar pressure calibrations in other gases, accurate data of enhancement factors have to be available. © 1998 Elsevier Science S.A. All rights reserved.

Pressure measurement

Bar (unit)

Hygrometer

Source

Cite

Citations (0)