James K. Luers

Use of Radiosonde Temperature Data in Climate Studies

Abstract Ten of the most common radiosondes used throughout the world since 1960 have been evaluated concerning potential use of their temperature data for climate studies. The VIZ; Space Data Corp.; Chinese GZZ; Japanese RS2-80; Russian RKZ, MARS, and A-22; and Vaisala RS80, RS 12/15, and RS18/21 radiosondes were evaluated by modeling the temperature of the sensing element relative to the temperature of the air in which it is immersed. The difference, designated as the temperature error, was calculated under various environmental conditions. Validation and sensitivity analysis studies were performed on each radiosonde model as a means of estimating the environmental parameters that influence the temperature error and the resulting accuracy of the day and nighttime temperature profiles. Environmental parameters to which some sondes were sensitive include cloud cover, surface temperature, solar angle, ambient temperature profile, blackbody temperature, and the ventilation velocity. The ventilation velocity...

Temperature corrections for the VIZ and VAISALA radiosondes

Abstract The National Weather Service VIZ radiosonde and the Vaisala RS-80 radiosondes are used worldwide to obtain upper-air measurements of atmospheric temperature and moisture. The temperature measured by each sensor is not equal to the atmospheric temperature due to solar and infrared irradiation of the sensor, heat conduction to the sensor from its attachment points, and radiation emitted by the sensor. Presently, only the RS-80 radiosonde applies corrections to the sensor temperature to compensate for these heating sources, and this correction is only considered to be a function of solar angle and pressure. Temperature correction models VIZCOR (VIZ sonde) and VAICOR (Vaisala RS-80 sonde) have been developed that derive the atmospheric temperature from the sensor temperature, taking into account all significant environmental processes that influence the beat transfer to the sensor. These models have been validated by comparing their corrected profiles with atmospheric temperature profiles derived fro...

CREATING CLIMATE REFERENCE DATASETS CARDS Workshop on Adjusting Radiosonde Temperature Data for Climate Monitoring

Homogeneous upper-air temperature time series are necessary for climate change detection and attribution. About 20 participants met at the National Climatic Data Center in Asheville, North Carolina on 11–12 October 2000 to discuss methods of adjusting radiosonde data for inhomogeneities arising from instrument and other changes. Representatives of several research groups described their methods for identifying change points and adjusting temperature time series and compared the results of applying these methods to data from 12 radiosonde stations. The limited agreement among these results and the potential impact of these adjustments on upper-air trends estimates indicate a need for further work in this area and for greater attention to homogeneity issues in planning future changes in radiosonde observations.

Unexplained Discontinuity in the U.S. Radiosonde Temperature Data. Part I: Troposphere

Inhomogeneities in U.S. radiosonde data that used the VIZ and Vaisala RS80 cannot be explained by radiation errors, which can be removed by the heat balance models. WMO intercomparision data, modeling results, temperature time series, and 1200 minus 0000 UTC temperature differences are examined to show that there appears to be an error in the U.S. RS80/RSN93 temperature correction software. Radiosonde soundings taken at U.S. stations that launch Vaisala RS80 radiosondes, which are integrated within the National Weather Service (NWS) Microcomputer Automatic Radio-Theodolite (Micro-ART) system, should not be used in climate studies since there is a large systematic error of unknown origin in the temperature data. This paper is the first of two and is primarily concerned with the midtroposphere. The second paper discusses the large unexplained 0000 and 1200 UTC differences in the stratosphere.

An evaluation of electrochemical concentration cell sonde measurements of atmospheric ozone

Abstract Using Dobson spectrophotometer measurements of total ozone as a comparison, an analysis of the Electrochemical Concentration Cell (ECC) ozonesondes measurement accuracy is presented. Days of conjunctive ECC-Dobson observations (from 1970 to 1976 at Wallops Flight Center) provide a set of 123 pairs of total ozone values. Sample set statistics are generated with means and standard deviations of total ozone values and differences being noted. An in-depth study of factors such as time differences between associated observations, integration techniques used, assumptions used in calculating residual ozone and other possible sources of errors are examined. Short-period changes in total ozone using Dobson data during the observational period are also described.

On Optimum Methods for Obtaining Wind Data from Balloon Sensors

Abstract A sinusoidal wind field is integrated to give the position of a sensor traveling with a constant vertical velocity. A linear least-squares smoothing technique is employed to calculate the velocity and acceleration of the sensor. The distortion of the computed wind field due to the smoothing technique is determined and a magnification factor is applied to compensate for this distortion. An expression is then derived for the error variance of the magnified computed wind field and this expression is minimized by the proper choice of the length of the smoothing interval. It is shown that for the ROBIN falling sphere the proper choice of both position and velocity smoothing intervals is 0.8 of the vertical wavelength of the wind field. In the case of a ROSE rising sphere the balloon velocity serves as an excellent approximation to the wind velocity. In this case, the optimum position smoothing interval is 0.8 of the vertical wavelength of the wind field.

The limitations of wind measurement accuracy for balloon systems

Abstract The error in horizontal wind field measurements as computed from the trajectory of balloons with linear and quadratic rise rates (as functions of altitude) has been derived. Balloon trajectories through light, moderate and severe wind fields have been considered. Figures are presented which show the wind error vs altitude for various rise rates in each wind field, assuming linear smoothing of the trajectory data. The rise rate profile of the Jimsphere is analyzed as a special case. The results and figures presented are useful in determining the ultimate capability of rising balloon systems in general and for the Jimsphere system in particular for measuring wind from the surface to 18 km. Using the figures presented, one can estimate the wind accuracy that can be achieved by any type of rising balloon by knowing only its rise rate behavior vs altitude. In addition, the results can be used in balloon design to determine what rise rate function is needed to achieve specified wind accuracies. A table...

Polynomial Smoothing-Linear VS Cubic*

Polynomial smoothing to estimate the derivative of a large sequence of sampled data requires the proper choice of the degree polynomial and the smoothing interval. Linear and cubic polynomial smoothing are compared. It is found that a linear polynomial will produce nearly the same first derivative as a cubic polynomial if the linear smoothing interval is properly chosen. A formula for the proper choice of the smoothing interval is derived. The technique is applied to a problem in meteorology and consistent results obtained.