Humidity measurements in cold and humid environments

Lasse Makkonen (Corresponding Author), Timo Laakso

Research output: Contribution to journalArticleScientificpeer-review

20 Citations (Scopus)

Abstract

Recent studies have shed new light on humidity conditions in the polar atmospheric boundary layer, and cast doubt on the reliability of humidity measurements above the frost point humidity. These issues are addressed herein by considering the processes that affect humidity and its measurement in cold climate conditions and by analyzing observations from two sites, at which the relative humidity is frequently above 100% at sub-freezing temperatures, as shown by repeatedly observed in-cloud icing events. Humidity measurements were made at these two sites by the commonly used Vaisala HMP35 probe and HMP233 capacitance probes respectively and simultaneously by the same manufacturer’s HMP243 probe that determines the frost point by a heated capacitance sensor. The results confirm that the relative humidity is frequently well above the frost point, both due to radiative cooling and to the advection of moist air, and that the conventional humidity measurements are unable to detect these events. Furthermore, after such events, the iced sensors show too high a humidity. The false values occur due to ice growth on the probe and cannot be corrected by any algorithm. Our results indicate that these problems, inherent to conventional humidity measurements in cold and humid environments, are avoided by the use of HMP243, which has a heated humidity probe.
Original languageEnglish
Pages (from-to)131 - 147
Number of pages17
JournalBoundary-Layer Meteorology
Volume116
Issue number1
DOIs
Publication statusPublished - 2005
MoE publication typeA1 Journal article-refereed

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humid environment
humidity
probe
frost
relative humidity
sensor
cold
climate conditions
freezing
advection
boundary layer
cooling
ice

Keywords

  • arctic boundary layer
  • frost point
  • humidity measurements
  • hygrometers
  • icing
  • relative humidity

Cite this

Makkonen, Lasse ; Laakso, Timo. / Humidity measurements in cold and humid environments. In: Boundary-Layer Meteorology. 2005 ; Vol. 116, No. 1. pp. 131 - 147.
@article{efacda7302c1450ea4ffad374d6a2ccd,
title = "Humidity measurements in cold and humid environments",
abstract = "Recent studies have shed new light on humidity conditions in the polar atmospheric boundary layer, and cast doubt on the reliability of humidity measurements above the frost point humidity. These issues are addressed herein by considering the processes that affect humidity and its measurement in cold climate conditions and by analyzing observations from two sites, at which the relative humidity is frequently above 100{\%} at sub-freezing temperatures, as shown by repeatedly observed in-cloud icing events. Humidity measurements were made at these two sites by the commonly used Vaisala HMP35 probe and HMP233 capacitance probes respectively and simultaneously by the same manufacturer’s HMP243 probe that determines the frost point by a heated capacitance sensor. The results confirm that the relative humidity is frequently well above the frost point, both due to radiative cooling and to the advection of moist air, and that the conventional humidity measurements are unable to detect these events. Furthermore, after such events, the iced sensors show too high a humidity. The false values occur due to ice growth on the probe and cannot be corrected by any algorithm. Our results indicate that these problems, inherent to conventional humidity measurements in cold and humid environments, are avoided by the use of HMP243, which has a heated humidity probe.",
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Humidity measurements in cold and humid environments. / Makkonen, Lasse (Corresponding Author); Laakso, Timo.

In: Boundary-Layer Meteorology, Vol. 116, No. 1, 2005, p. 131 - 147.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Humidity measurements in cold and humid environments

AU - Makkonen, Lasse

AU - Laakso, Timo

N1 - Project code: R3SU00580

PY - 2005

Y1 - 2005

N2 - Recent studies have shed new light on humidity conditions in the polar atmospheric boundary layer, and cast doubt on the reliability of humidity measurements above the frost point humidity. These issues are addressed herein by considering the processes that affect humidity and its measurement in cold climate conditions and by analyzing observations from two sites, at which the relative humidity is frequently above 100% at sub-freezing temperatures, as shown by repeatedly observed in-cloud icing events. Humidity measurements were made at these two sites by the commonly used Vaisala HMP35 probe and HMP233 capacitance probes respectively and simultaneously by the same manufacturer’s HMP243 probe that determines the frost point by a heated capacitance sensor. The results confirm that the relative humidity is frequently well above the frost point, both due to radiative cooling and to the advection of moist air, and that the conventional humidity measurements are unable to detect these events. Furthermore, after such events, the iced sensors show too high a humidity. The false values occur due to ice growth on the probe and cannot be corrected by any algorithm. Our results indicate that these problems, inherent to conventional humidity measurements in cold and humid environments, are avoided by the use of HMP243, which has a heated humidity probe.

AB - Recent studies have shed new light on humidity conditions in the polar atmospheric boundary layer, and cast doubt on the reliability of humidity measurements above the frost point humidity. These issues are addressed herein by considering the processes that affect humidity and its measurement in cold climate conditions and by analyzing observations from two sites, at which the relative humidity is frequently above 100% at sub-freezing temperatures, as shown by repeatedly observed in-cloud icing events. Humidity measurements were made at these two sites by the commonly used Vaisala HMP35 probe and HMP233 capacitance probes respectively and simultaneously by the same manufacturer’s HMP243 probe that determines the frost point by a heated capacitance sensor. The results confirm that the relative humidity is frequently well above the frost point, both due to radiative cooling and to the advection of moist air, and that the conventional humidity measurements are unable to detect these events. Furthermore, after such events, the iced sensors show too high a humidity. The false values occur due to ice growth on the probe and cannot be corrected by any algorithm. Our results indicate that these problems, inherent to conventional humidity measurements in cold and humid environments, are avoided by the use of HMP243, which has a heated humidity probe.

KW - arctic boundary layer

KW - frost point

KW - humidity measurements

KW - hygrometers

KW - icing

KW - relative humidity

U2 - 10.1007/s10546-004-7955-y

DO - 10.1007/s10546-004-7955-y

M3 - Article

VL - 116

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SN - 0006-8314

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