scholarly journals An inexpensive and stable LED Sun photometer for measuring the water vapor column over South Texas from 1990 to 2001

2002 ◽  
Vol 29 (13) ◽  
Author(s):  
Forrest M. Mims
Keyword(s):  
Water Vapor ◽  
South Texas ◽  
Sun Photometer

Raman Lidar and Sun Photometer Measurements of Aerosols and Water Vapor

1997 ◽  
pp. 23-26 ◽  
Author(s):  
R. A. Ferrare ◽  
S. H. Melfi ◽  
D. Whiteman ◽  
K. D. Evans ◽  
G. Schwemmer ◽  
...  
Keyword(s):  
Water Vapor ◽  
Raman Lidar ◽  
Sun Photometer

Total water vapor content retrieval from sun photometer data

2013 ◽  
Vol 26 (4) ◽  
pp. 281-284 ◽  
Author(s):  
K. M. Firsov ◽  
T. Yu. Chesnokova ◽  
E. V. Bobrov ◽  
I. I. Klitochenko
Keyword(s):  
Water Vapor ◽  
Water Vapor Content ◽  
Total Water ◽  
Content Retrieval ◽  
Sun Photometer

scholarly journals Calibration of Raman lidar water vapor profiles by means of AERONET photometer observations and GDAS meteorological data

2018 ◽  
Vol 11 (5) ◽  
pp. 2735-2748 ◽  
Author(s):  
Guangyao Dai ◽  
Dietrich Althausen ◽  
Julian Hofer ◽  
Ronny Engelmann ◽  
Patric Seifert ◽  
...  
Keyword(s):  
Water Vapor ◽  
Precipitable Water ◽  
Precipitable Water Vapor ◽  
The Sun ◽  
Mixing Ratio ◽  
Raman Lidar ◽  
Pressure Profiles ◽  
Sun Photometer ◽  
Water Vapor Mixing Ratio ◽  
Lidar Observations

Abstract. We present a practical method to continuously calibrate Raman lidar observations of water vapor mixing ratio profiles. The water vapor profile measured with the multiwavelength polarization Raman lidar PollyXT is calibrated by means of co-located AErosol RObotic NETwork (AERONET) sun photometer observations and Global Data Assimilation System (GDAS) temperature and pressure profiles. This method is applied to lidar observations conducted during the Cyprus Cloud Aerosol and Rain Experiment (CyCARE) in Limassol, Cyprus. We use the GDAS temperature and pressure profiles to retrieve the water vapor density. In the next step, the precipitable water vapor from the lidar observations is used for the calibration of the lidar measurements with the sun photometer measurements. The retrieved calibrated water vapor mixing ratio from the lidar measurements has a relative uncertainty of 11 % in which the error is mainly caused by the error of the sun photometer measurements. During CyCARE, nine measurement cases with cloud-free and stable meteorological conditions are selected to calculate the precipitable water vapor from the lidar and the sun photometer observations. The ratio of these two precipitable water vapor values yields the water vapor calibration constant. The calibration constant for the PollyXT Raman lidar is 6.56 g kg−1 ± 0.72 g kg−1 (with a statistical uncertainty of 0.08 g kg−1 and an instrumental uncertainty of 0.72 g kg−1). To check the quality of the water vapor calibration, the water vapor mixing ratio profiles from the simultaneous nighttime observations with Raman lidar and Vaisala radiosonde sounding are compared. The correlation of the water vapor mixing ratios from these two instruments is determined by using all of the 19 simultaneous nighttime measurements during CyCARE. Excellent agreement with the slope of 1.01 and the R2 of 0.99 is found. One example is presented to demonstrate the full potential of a well-calibrated Raman lidar. The relative humidity profiles from lidar, GDAS (simulation) and radiosonde are compared, too. It is found that the combination of water vapor mixing ratio and GDAS temperature profiles allow us to derive relative humidity profiles with the relative uncertainty of 10–20 %.

Measuring Total Column Water Vapor by Pointing an Infrared Thermometer at the Sky

2011 ◽  
Vol 92 (10) ◽  
pp. 1311-1320 ◽  
Author(s):  
Forrest M. Mims ◽  
Lin Hartung Chambers ◽  
David R. Brooks
Keyword(s):  
Water Vapor ◽  
Precipitable Water ◽  
Infrared Thermometer ◽  
Coefficient Of Correlation ◽  
Mauna Loa ◽  
South Central ◽  
Central Texas ◽  
Solar Noon ◽  
Sun Photometer ◽  
Total Column

A 2-yr study affirms that the temperature indicated by an inexpensive ($20–$60) IR thermometer pointed at the cloud-free zenith sky (Tz) is a proxy for total column water vapor [precipitable water (PW)]. From 8 September 2008 to 18 October 2010 Tz was measured either at or near solar noon, and occasionally at night, at a field in south-central Texas. PW was measured by a MICROTOPS II sun photometer. The coefficient of correlation (r2) of PW and Tz was 0.90, and the rms difference was 3.2 mm. A comparison of Tz with PW from a GPS site 31 km northnortheast yielded an r2 of 0.79 and an rms difference of 5.8 mm. An expanded study compared Tz from eight IR thermometers with PW at various times during the day and night from 17 May to 18 October 2010, mainly at the Texas site, with an additional 10 days at Hawaii's Mauna Loa Observatory. The best results were provided by two IR thermometers that yielded an r2 of 0.96 and an rms difference with PW of 2.7 mm. The results of both the ongoing 2-yr study and the 5-month comparison show that IR thermometers can measure PW with an accuracy (rms difference/mean PW) approaching 10%, which is the accuracy typically ascribed to sun photometers. The simpler IR method, which works during both day and night, can be easily mastered by students, amateur scientists, and cooperative weather observers.

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