(1) to other pressures, however, how much error can one expect? The error is indicated in Fig. Also, because the regression equation is only a statistical fit and is not based on physical principles, one cannot assume that it would be valid at other pressures. Pressure was not used as one of the predictor variables, and hence the resulting regression does not vary with pressure. The input data for this regression were only T w, T, and RH% for standard sea level pressure of 101.325 kPa. GEP can explore a wide range of the function space to find a best fit and can yield a nonlinear result that would not necessarily have been obvious if the function fit had been attempted manually. Details of GEP for meteorological applications are presented by Bakhshaii and Stull (2009) and Roebber (2010).
#Dry bulb and wet bulb humidity ratio calculator verification#
GEP ( Ferreira 2006) is an efficient variant of genetic programming, in which candidate functions evolve through various forms of mutation and compete by a computational natural selection until the fittest candidate (with the lowest verification error) is found. Gene-expression programming (GEP) was the method used to find a best-fit function to the data. 2 and 3, T w from the regression equation can quickly diverge from reality. Outside the valid region plotted in Figs. Thus, the T w errors have multiple relative maxima and minima of order from −1.0° to +0.6☌, with larger errors generally near the edges of the valid domain.
![dry bulb and wet bulb humidity ratio calculator dry bulb and wet bulb humidity ratio calculator](https://promart.vteximg.com.br/arquivos/ids/521093-444-444/104167.jpg)
The second factor is that the regression is highly nonlinear and is not based on physical principles. 3 is outlined with the dashed line in Fig. 3, for which the regression does not apply. 1, for which no data are provided, corresponds to the region in the lower-left corner of Fig. Thus, the region of cold temperatures and low relative humidities in the lower-right corner of Fig. One is that the regression was based only on the data from Fig. In a similar way, sometimes it is desirable to estimate T w without using Normand’s rule ( Stull 2011) on a thermodynamic diagram.įigures 2 and 3 are plotted on the same scale so that at any point ( T, RH%) one can find T w from Fig. Wet-bulb temperature T w and wet-bulb potential temperature can be used to label saturated adiabats on thermodynamic diagrams such as skew Ts and tephigrams ( Stull 2011). Lower T w allows industrial cooling towers and other evaporative coolers (also called swamp coolers or desert coolers) to operate more efficiently (see ). In a similar way, subzero T w values can exacerbate freezing-rain events. The effectiveness of snowmaking equipment is a strong function of T w, because snow can be produced in air temperatures slightly above freezing if T w is below about −2☌ (see, e.g., online at ). For example, the “wet-bulb globe temperature” is used by industrial hygienists, athletes, and the military to estimate the composite effect of temperature, solar radiation, humidity, and wind speed on people (see, e.g., online at ). Yet some applications require estimates of T w, given electronic sensor measurements or numerical forecasts of T and RH%. The empirical fit is not valid in the black-shaded region.
![dry bulb and wet bulb humidity ratio calculator dry bulb and wet bulb humidity ratio calculator](https://4.bp.blogspot.com/-UW5axBVgzh0/WrkxW_cX69I/AAAAAAAADHY/LzLP0IONTfQX5erLphUE4CbciV-eQhaawCLcBGAs/s1600/04%2B-%2BPSYCH%2BCHART%2B-%2BWBT%2BLINES%2B%28800p%29.jpg)
Gray shading highlights near-zero errors.
![dry bulb and wet bulb humidity ratio calculator dry bulb and wet bulb humidity ratio calculator](https://www.picodogaviao.esp.br/wp-content/uploads/2021/11/seme-ar-1024x865.jpg)
(1) is applied to pressures that are not equal to 101.325 kPa. These gray curves are useful for estimating the error if Eq. The gray curves associated with each T w are for P = 80 kPa (thinner lines) and P = 60 kPa (thinnest lines, located farther away from each black line).
![dry bulb and wet bulb humidity ratio calculator dry bulb and wet bulb humidity ratio calculator](https://cdn.instrumentationtools.com/wp-content/uploads/2015/12/instrumentationtools.com_humidity-calculator.png)
The valid range is enclosed by a dashed line, and the valid pressure is 101.325 kPa. Isopleths of T w (thick black curves) vs RH% and T, found from Eq. In the saturation calculation to determine relative humidity, Teten’s equation was used to account for variations in latent heat of vaporization ( Stull 2011). The abscissa changes scale at the dark vertical lines. Psychrometric graph for standard sea level pressure of 101.325 kPa.