scholarly journals Comparisons of temperature, pressure and humidity measurements by balloon-borne radiosondes and frost point hygrometers during MOHAVE 2009

2011 ◽  
Vol 4 (4) ◽  
pp. 4357-4401 ◽  
Author(s):  
D. F. Hurst ◽  
E. G. Hall ◽  
A. F. Jordan ◽  
L. M. Miloshevich ◽  
D. N. Whiteman ◽  
...  
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Mixing Ratios ◽  
Frost Point ◽  
Humidity Measurements ◽  
Large Measurement ◽  
Measurement Uncertainties ◽  
Temperature And Pressure ◽  
Measurement Biases

Abstract. We compare coincident, balloon-borne, in situ measurements of temperature and pressure by two radiosondes (Vaisala RS92, Intermet iMet-1-RSB) and measurements of relative humidity (RH) by Vaisala RS92 sondes and frost point hygrometers. Data from a total of 28 balloon flights with mixed payloads are analyzed in 1-km altitude bins to quantify measurement biases between sensors and how they vary with altitude. The disparities between sensors determined here are compared to measurement uncertainties quoted by the two radiosonde manufacturers. Our comparisons expose several flight profiles with anomalously large measurement differences. Excluding these anomalous profiles, 33 % of RS92-iMet median temperature differences exceed the uncertainty limits calculated from manufacturer-quoted uncertainties. A statistically significant, altitude-independent bias of about 0.5 ± 0.2 °C is revealed for the RS92-iMet temperature differences. Similarly, 23 % of RS92-iMet median pressure differences exceed the quoted uncertainty limits, with 83 % of these excessive differences above 16 km altitude. The pressure differences are altitude dependent, increasing from −0.6 ± 0.9 hPa at the surface to 0.7 ± 0.1 hPa above 15 km. Temperature and pressure differences between redundant RS92 sondes on the same balloon exceed manufacturer-quoted reproducibility limits 20 % and 2 % of the time, respectively, with most of the excessive differences belonging to anomalous difference profiles. Relative humidity measurements by RS92 sondes are compared to other RS92 sondes and to RH values calculated using frost point hygrometer measurements and coincident radiosonde temperature measurements. For some flights the RH differences are anomalously large, but in general are within the ±5 % RH measurement uncertainty limits quoted for the RS92. The quantitative effects of RS92 and iMet pressure and temperature differences on frost point-based water vapor mixing ratios and RH values, respectively, are also presented.

scholarly journals Comparisons of temperature, pressure and humidity measurements by balloon-borne radiosondes and frost point hygrometers during MOHAVE-2009

2011 ◽  
Vol 4 (12) ◽  
pp. 2777-2793 ◽  
Author(s):  
D. F. Hurst ◽  
E. G. Hall ◽  
A. F. Jordan ◽  
L. M. Miloshevich ◽  
D. N. Whiteman ◽  
...  
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Measurement Uncertainty ◽  
Mixing Ratios ◽  
Frost Point ◽  
Measurement Reproducibility ◽  
Humidity Measurements ◽  
Large Measurement ◽  
Reproducibility Limit

Abstract. We compare coincident, in situ, balloon-borne measurements of temperature (T) and pressure (P) by two radiosondes (Vaisala RS92, Intermet iMet-1-RSB) and similar measurements of relative humidity (RH) by RS92 sondes and frost point hygrometers. Data from a total of 28 balloon flights with at least one pair of radiosondes are analyzed in 1-km altitude bins to quantify measurement differences between the sonde sensors and how they vary with altitude. Each comparison (T, P, RH) exposes several profiles of anomalously large measurement differences. Measurement difference statistics, calculated with and without the anomalous profiles, are compared to uncertainties quoted by the radiosonde manufacturers. Excluding seven anomalous profiles, T differences between 19 pairs of RS92 and iMet sondes exceed their measurement uncertainty limits (2 σ) 31% of the time and reveal a statistically significant, altitude-independent bias of 0.5 ± 0.2 °C. Similarly, RS92-iMet P differences in 22 non-anomalous profiles exceed their uncertainty limits 23% of the time, with a disproportionate 83% of the excessive P differences at altitudes >16 km. The RS92-iMet pressure differences increase smoothly from −0.6 hPa near the surface to 0.8 hPa above 25 km. Temperature and P differences between all 14 pairs of RS92 sondes exceed manufacturer-quoted, reproducibility limits (σ) 28% and 11% of the time, respectively. About 95% of the excessive T differences are eliminated when 5 anomalous RS92-RS92 profiles are excluded. Only 5% of RH measurement differences between 14 pairs of RS92 sondes exceed the manufacturer's measurement reproducibility limit (σ). RH measurements by RS92 sondes are also compared to RH values calculated from frost point hygrometer measurements and coincident T measurements by the radiosondes. The influences of RS92-iMet Tand P differences on RH values and water vapor mixing ratios calculated from frost point hygrometer measurements are examined.

scholarly journals Two decades of water vapor measurements with the FISH fluorescence hygrometer: a review

2015 ◽  
Vol 15 (14) ◽  
pp. 8521-8538 ◽  
Author(s):  
J. Meyer ◽  
C. Rolf ◽  
C. Schiller ◽  
S. Rohs ◽  
N. Spelten ◽  
...  
Keyword(s):  
Water Vapor ◽  
High Pressures ◽  
Calibration Procedure ◽  
Atmospheric Conditions ◽  
Total Water ◽  
Mixing Ratios ◽  
Frost Point ◽  
In Situ Observations ◽  
Quality Check

Abstract. For almost two decades, the airborne Fast In-situ Stratospheric Hygrometer (FISH) has stood for accurate and precise measurements of total water mixing ratios (WMR, gas phase + evaporated ice) in the upper troposphere and lower stratosphere (UT/LS). Here, we present a comprehensive review of the measurement technique (Lyman-α photofragment fluorescence), calibration procedure, accuracy and reliability of FISH. Crucial for FISH measurement quality is the regular calibration to a water vapor reference, namely the commercial frost-point hygrometer DP30. In the frame of this work this frost-point hygrometer is compared to German and British traceable metrological water standards and its accuracy is found to be 2–4 %. Overall, in the range from 4 to 1000 ppmv, the total accuracy of FISH was found to be 6–8 %, as stated in previous publications. For lower mixing ratios down to 1 ppmv, the uncertainty reaches a lower limit of 0.3 ppmv. For specific, non-atmospheric conditions, as set in experiments at the AIDA chamber – namely mixing ratios below 10 and above 100 ppmv in combination with high- and low-pressure conditions – the need to apply a modified FISH calibration evaluation has been identified. The new evaluation improves the agreement of FISH with other hygrometers to ± 10 % accuracy in the respective mixing ratio ranges. Furthermore, a quality check procedure for high total water measurements in cirrus clouds at high pressures (400–500 hPa) is introduced. The performance of FISH in the field is assessed by reviewing intercomparisons of FISH water vapor data with other in situ and remote sensing hygrometers over the last two decades. We find that the agreement of FISH with the other hygrometers has improved over that time span from overall up to ± 30 % or more to about ± 5–20 % @ < 10 ppmv and to ± 0–15 % @ > 10 ppmv. As presented here, the robust and continuous calibration and operation procedures of the FISH instrument over the last two decades establish the position of FISH as one of the core instruments for in situ observations of water vapor in the UT/LS.

scholarly journals Intercomparison of midlatitude tropospheric and lower-stratospheric water vapor measurements and comparison to ECMWF humidity data

2018 ◽  
Vol 18 (22) ◽  
pp. 16729-16745 ◽  
Author(s):  
Stefan Kaufmann ◽  
Christiane Voigt ◽  
Romy Heller ◽  
Tina Jurkat-Witschas ◽  
Martina Krämer ◽  
...  
Keyword(s):  
Water Vapor ◽  
Climate Impact ◽  
Cloud Formation ◽  
Mean Values ◽  
Stratospheric Water Vapor ◽  
Mixing Ratios ◽  
Quality Of Water ◽  
Research Aircraft ◽  
German Aerospace

Abstract. Accurate measurement of water vapor in the climate-sensitive region near the tropopause is very challenging. Unexplained systematic discrepancies between measurements at low water vapor mixing ratios made by different instruments on airborne platforms have limited our ability to adequately address a number of relevant scientific questions on the humidity distribution, cloud formation and climate impact in that region. Therefore, during the past decade, the scientific community has undertaken substantial efforts to understand these discrepancies and improve the quality of water vapor measurements. This study presents a comprehensive intercomparison of airborne state-of-the-art in situ hygrometers deployed on board the DLR (German Aerospace Center) research aircraft HALO (High Altitude and LOng Range Research Aircraft) during the Midlatitude CIRRUS (ML-CIRRUS) campaign conducted in 2014 over central Europe. The instrument intercomparison shows that the hygrometer measurements agree within their combined accuracy (±10 % to 15 %, depending on the humidity regime); total mean values agree within 2.5 %. However, systematic differences on the order of 10 % and up to a maximum of 15 % are found for mixing ratios below 10 parts per million (ppm) H2O. A comparison of relative humidity within cirrus clouds does not indicate a systematic instrument bias in either water vapor or temperature measurements in the upper troposphere. Furthermore, in situ measurements are compared to model data from the European Centre for Medium-Range Weather Forecasts (ECMWF) which are interpolated along the ML-CIRRUS flight tracks. We find a mean agreement within ±10 % throughout the troposphere and a significant wet bias in the model on the order of 100 % to 150 % in the stratosphere close to the tropopause. Consistent with previous studies, this analysis indicates that the model deficit is mainly caused by too weak of a humidity gradient at the tropopause.

scholarly journals Intercomparison of mid-latitude tropospheric and lower stratospheric water vapor measurements and comparison to ECMWF humidity data

2018 ◽  
Author(s):  
Stefan Kaufmann ◽  
Christiane Voigt ◽  
Romy Heller ◽  
Tina Jurkat-Witschas ◽  
Martina Krämer ◽  
...  
Keyword(s):  
Water Vapor ◽  
Climate Impact ◽  
Cloud Formation ◽  
Mean Values ◽  
Stratospheric Water Vapor ◽  
Mixing Ratios ◽  
Quality Of Water ◽  
Research Aircraft ◽  
German Aerospace

Abstract. Accurate measurement of water vapor in the climate sensitive region near the tropopause turned out to be very challenging. Unexplained systematic discrepancies between measurements at low water vapor mixing ratios made by different instruments on airborne platforms have limited our ability to adequately address a number relevant scientific questions on the humidity distribution, cloud formation and climate impact in that region. Therefore, during the past decade, the scientific community has undertaken substantial efforts to understand these discrepancies and improve the quality of water vapor measurements. This study presents a comprehensive intercomparison of airborne state-of-the-art in situ hygrometers deployed onboard the DLR (German Aerospace Center) research aircraft HALO during the Mid-Latitude CIRRUS (ML-CIRRUS) campaign conducted in 2014 over central Europe. The instrument intercomparison shows that the hygrometer measurements agree within their combined accuracy (±10 to 15 %, depending on the humidity regime), total mean values even agree within 2.5 %. However, systematic differences on the order of 10 % and up to a maximum of 15 % are found for mixing ratios below 10 parts per million (ppm) H2O. A comparison of relative humidity within cirrus clouds does not indicate a systematic instrument bias in either water vapor or temperature measurements in the upper troposphere. Furthermore, in situ measurements are compared to model data from the European Centre for Medium-Range Weather Forecasts (ECMWF) which are interpolated along the ML-CIRRUS flight tracks. We find a mean agreement within ±10 % throughout the troposphere and a significant wet bias in the model on the order of 100 % to 150 % in the stratosphere close to the tropopause. Consistent with previous studies, this analysis indicates that the model deficit is mainly caused by a blurred humidity gradient at tropopause altitudes.

scholarly journals Characterization and Corrections of Relative Humidity Measurement from Meteomodem M10 Radiosondes at Midlatitude Stations

2020 ◽  
Vol 37 (5) ◽  
pp. 857-871
Author(s):  
Jean-Charles Dupont ◽  
Martial Haeffelin ◽  
Jordi Badosa ◽  
Gaelle Clain ◽  
Christophe Raux ◽  
...  
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Humidity Sensor ◽  
Global Climate ◽  
Time Lag ◽  
Capacitive Sensor ◽  
Cold Temperatures ◽  
Humidity Measurements ◽  
Main Effects ◽  
Very High

AbstractMeasurement of water vapor or humidity in the atmosphere is fundamental for many applications. Relative humidity measurements with a capacitive sensor in radiosondes are affected by several factors that need to be assessed and corrected. This work aims to address corrections for the main effects for the Meteomodem M10 radiosonde as a step to meet the Global Climate Observing System (GCOS) Reference Upper-Air Network (GRUAN) requirements. The considered corrections are 1) the calibration correction; 2) a slow regime due to the slow diffusion of molecules through the sensor, especially at very high and very low relative humidity conditions; 3) the relative humidity sensor dependence on the gradient of temperature; and 4) the time lag at cold temperatures, which affects measurements in regions of strong relative humidity gradients. These corrections were tested for 26 nighttime and 25 daytime radiosondes in two midlatitude locations for which both Meteomodem M10 and Vaisala RS92 measurements were available. The results show that, after correcting for the four effects, M10 relative humidity measurements are, on average, consistent with the Vaisala RS92 relative humidity values within 2% RH at all altitudes for the nighttime launches (against 6% RH before the correction) and within 5% RH at all altitudes for the daytime launches (against 9% RH before the correction).

scholarly journals Variability of Stratospheric Water Vapor Inferred from SAGE II, HALOE, and Boulder (Colorado) Balloon Measurements

2006 ◽  
Vol 19 (16) ◽  
pp. 4121-4133 ◽  
Author(s):  
E. W. Chiou ◽  
L. W. Thomason ◽  
W. P. Chu
Keyword(s):  
Water Vapor ◽  
Correlation Coefficients ◽  
Quantitative Agreement ◽  
Stratospheric Aerosol ◽  
Stratospheric Water Vapor ◽  
Mixing Ratios ◽  
Frost Point ◽  
The North ◽  
Low Latitudes ◽  
Balloon Measurements

Abstract The variability of stratospheric water vapor between 1996 and 2004 has been studied using multiyear measurements from the Stratospheric Aerosol and Gas Experiment II (SAGE II) version 6.2 dataset, the Halogen Occultation Experiment (HALOE) version 19 dataset, and the balloon-borne frost point hygrometer data record at Boulder, Colorado (40°N, 105°W). The features derived from SAGE II and HALOE for 20° latitudinal zones from 60°S to 60°N at various altitudes (16–34 km) show good quantitative agreement regarding the phases and magnitudes of annual, semiannual, and quasi-biennial oscillations (QBO). For the latitudinal zones 20°–40° and 40°–60°, the hemispheric asymmetry at 22 km with mainly QBO in the north and predominantly annual oscillations in the south has been revealed by both SAGE II and HALOE observations. Strong correlation exists between SAGE II and HALOE lower-stratospheric H2O anomalies over low latitudes and 100-hPa tropical zonal mean temperature anomalies. The correlation coefficients based on the 0°–20°S water vapor time series with H2O lagged by 2 months are 0.81 and 0.70 for HALOE and SAGE II, respectively. For 35°–45°N, SAGE II and HALOE show consistent trends generally varying from −0.05 to −0.02 ppmv yr−1 between 16 and 34 km. The corresponding analyses based on frost point measurements over Boulder show insignificant trends. These trends are not strongly dependent on the end points of the analysis and stand in contrast to the positive trends reported in previous studies that include data records prior to 1994. For the lower stratosphere, investigations of the entire balloon-borne dataset over Boulder indicate higher values of mixing ratios after 1992–93 compared to the period 1980–92. In contrast, SAGE II monthly zonal mean measurements for 35°–45°N show insignificant differences between the periods 1987–89 and 1996–2004.

scholarly journals Dewpoint and Humidity Measurements and Trends at the Summit of Mount Washington, New Hampshire, 1935–2004

2007 ◽  
Vol 20 (22) ◽  
pp. 5629-5641 ◽  
Author(s):  
Thomas M. Seidel ◽  
Andrea N. Grant ◽  
Alexander A. P. Pszenny ◽  
Daniel J. Allman
Keyword(s):  
Relative Humidity ◽  
New Hampshire ◽  
Mixing Ratio ◽  
Dewpoint Temperature ◽  
Full Study ◽  
Humidity Measurements ◽  
Annual Frequency ◽  
Temperature And Pressure ◽  
Water Vapor Mixing Ratio ◽  
Mount Washington

Abstract Meteorological conditions have been recorded at the summit of Mount Washington, New Hampshire, (44°16′N, 71°18′W, 1914 m ASL) since November 1932. Use of consistent instrumentation allows analysis of humidity measurements as calculated from error-checked dry bulb temperature, wet bulb temperature, and pressure during the period 1935–2004. This paper presents seasonally and annually averaged dewpoint temperature, mixing ratio, and relative humidity means and trends, including clear-air and fog subsets and, beginning in 1939, day and night subsets. The majority of linear trends are negative over the full study period, although these decreases are not constant, with relatively large (small) values in the mid-1950s (late 1970s). Annual mean dewpoint (water vapor mixing ratio) over the 70-yr period has decreased by 0.06°C decade−1 (0.01 g kg−1 decade−1). During this period the annual frequency of fog increased by 0.5% decade−1. Dewpoint and mixing ratio trends, both generally decreasing, differ by season; they are smallest in spring and greatest in fall. Relative humidity has decreased most in winter. The clear-air subset shows significant decreases in both dewpoint and mixing ratio for all seasons except spring.

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

2010 ◽  
Vol 3 (2) ◽  
pp. 1263-1301 ◽  
Author(s):  
L. Yurganov ◽  
W. McMillan ◽  
C. Wilson ◽  
M. Fischer ◽  
S. Biraud
Keyword(s):  
Boundary Layer ◽  
Water Vapor ◽  
Great Plains ◽  
A Priori ◽  
Microwave Radiometer ◽  
Precipitable Water ◽  
Diurnal Cycles ◽  
Mixing Ratios ◽  
True Profile

Abstract. CO mixing ratios weighted over the bottom 2-km thick atmospheric layer between 2002 and 2009 were retrieved from downwelling infrared (IR) radiance spectra of the clear sky measured 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 the algorithm proposed by He at al. (2001) was significantly improved and validated. Essentially, the new algorithm retrieves a CO mixing ratio that is determined by the convolution of the a priori profile (assumed to be constant with altitude), the true profile, and the averaging kernel which maximizes near the surface. Approximately 70% of the CO signal comes from the boundary layer and the remaining 30% come from the lower part of the free troposphere. 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. Additionally, a correction for scattered solar light was developed. The retrieved CO was validated using simultaneous independently measured CO profiles. An aircraft supplied in situ CO measurements at altitudes up to 4572 m above sea level once or twice a week between March 2006 and December 2008. The aircraft measurements were supplemented with ground-based CO measurements at the SGP and retrievals from the Atmospheric IR Sounder (AIRS) above 5 km to create full tropospheric CO profiles. Comparison of the convolved profiles 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 AERI are compared with those measured continuously in situ at the SGP in the boundary layer. Monthly mean CO values measured by AERI between 2002 and 2009 are compared with those measured by AIRS over North America, the Northern Hemisphere mid-latitudes, and over the tropics.

scholarly journals Climatic controls on water vapor deuterium excess in the marine boundary layer of the North Atlantic based on 500 days of in situ, continuous measurements

2014 ◽  
Vol 14 (2) ◽  
pp. 2363-2401 ◽  
Author(s):  
H. C. Steen-Larsen ◽  
A. E. Sveinbjörnsdottir ◽  
A. J. Peters ◽  
V. Masson-Delmotte ◽  
M. P. Guishard ◽  
...  
Keyword(s):  
Water Vapor ◽  
Wind Speed ◽  
Relative Humidity ◽  
North Atlantic ◽  
Deuterium Excess ◽  
The North ◽  
Hourly Data ◽  
The North Atlantic ◽  
The Relationship

Abstract. Continuous, in situ measurements of water vapor isotopic composition have been conducted in the North Atlantic, Bermuda Islands (32.26° N, 64.88° W) between November 2011 and June~2013, using a~cavity-ring-down-spectrometer water vapor isotope analyzer and an autonomous self-designed calibration system. Meticulous calibration allows us to reach an accuracy and precision on 10 min average of δ18O, δD, and d-excess of respectively 0.14 ‰, 0.85 ‰, and 1.1 ‰, verified using two parallel instruments with independent calibration. As a result of more than 500 days with 6 hourly data the relationships between deuterium excess, relative humidity (rh), sea surface temperature (SST), wind speed and direction are assessed. From the whole dataset, 84% of d-excess variance is explained by a strong linear relationship with relative humidity. The slope of this relationship (−42.6 ± 0.4 ‰ % (rh)) is similar to the theoretical prediction of Merlivat and Jouzel (1979) for SST between 20 °C and 30 °C. However, in contrast with theory, no effect of wind speed could be detected on the relationship between d-excess and relative humidity. Separating the dataset into winter, spring, summer, and autumn seasons reveals different linear relationships between d-excess and humidity. Changes in wind directions are observed to affect the relationships between d-excess and humidity. The observed seasonal variability in the relationship between d-excess and relative humidity underlines the importance of long-term monitoring to make accurate conclusions.

scholarly journals Climatic controls on water vapor deuterium excess in the marine boundary layer of the North Atlantic based on 500 days of in situ, continuous measurements

2014 ◽  
Vol 14 (15) ◽  
pp. 7741-7756 ◽  
Author(s):  
H. C. Steen-Larsen ◽  
A. E. Sveinbjörnsdottir ◽  
A. J. Peters ◽  
V. Masson-Delmotte ◽  
M. P. Guishard ◽  
...  
Keyword(s):  
Water Vapor ◽  
Wind Speed ◽  
Relative Humidity ◽  
North Atlantic ◽  
Deuterium Excess ◽  
Data Set ◽  
The North ◽  
The North Atlantic ◽  
The Relationship

Abstract. Continuous, in situ measurements of water vapor isotopic composition have been conducted in the North Atlantic, at the Bermuda Islands (32.26° N, 64.88° W), between November 2011 and June 2013, using a cavity ring-down spectrometer water vapor isotope analyzer and an autonomous self-designed calibration system. Meticulous calibration allows us to reach an accuracy and precision on 10 min average of δ18O, δ D, and d-excess of, 0.14, 0.85, and 1.1‰, verified using two parallel instruments with independent calibration. As a result of more than 500 days with 6-hourly data the relationships between deuterium excess, relative humidity (RH), sea surface temperature (SST), wind speed, and wind direction are assessed. From the whole data set, 84 % of d-excess variance is explained by a strong linear relationship with relative humidity. The slope of this relationship (−42.6 ± 0.4‰ % (RH)) is similar to the theoretical prediction of Merlivat and Jouzel (1979) for SST between 20 and 30 °C. However, in contrast with theory, no effect of wind speed could be detected on the relationship between d-excess and relative humidity. Separating the data set into winter, spring, summer, and autumn seasons reveals different linear relationships between d-excess and humidity. Changes in wind directions are observed to affect the relationships between d-excess and humidity. The observed seasonal variability in the relationship between d-excess and relative humidity underlines the importance of long-term monitoring to make accurate conclusions.

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