Relationship between Types of Precipitation on the Ground and Surface Meteorological Elements

Abstract

Routine surface meteorological data at three weather stations in Japan, i.e., Wajima (sea shore), Matsumoto (inland), and Nikko (inland), were analyzed in order to obtain the relationship between the occurrence of the types of precipitation of snow, sleet, and rain on the ground and surface meteorological elements. The results indicate that the types of precipitation were dependent on surface relative humidity as well as surface air temperature. Even at the same air temperature, the precipitation types varied depending on humidity, and that critically. Two critical humidities were recognized at a given air temperature and the precipitation types were characterized by these critical humidities. Below a lower critical humidity, precipitations were all snow. Within some range above the critical humidity, they could be snow, sleet, or rain. Above a higher critical humidity on the top of the range, only rains were observed. These facts suggest that melting of snowflakes proceeds rapidly at higher relative humidity.From statistical analyses, two critical humidities for snow and rain (%) were obtained as a function of surface air temperature (*).The obtained relations at each station were as follows:, RHcri (snow) = -7.5T+93, RHcri (rain) =46*6.2 -T , Wajima RHcri (snow)=-7.3T+96, RHcri (rain)=39*7.2-T, Matsumoto RHcri (snow)=-6.2T+91, RHcri (rain)=43*6.8-T, Nikkowhere RHcri (snow) is a lower critical humidity and RHcri (rain) a higher critical one. The relations for snow are hardly different among the observation stations, but those for rain are different. The difference of the relations for rain suggests that the size and density of snowflakes are different from station to station and that the difference affects the speed of the generation of raindrops due to melting. The non-difference of the relations for snow, on the other hand, suggests that the, difference in physical properties of snowflakes does not exert any influence on the relations for snow.Sleet was obtained in the transition region surrounded by two relations for snow and rain and its occurrence was associated with high precipitation rate together with air temperature and humidity.These analytical results are explained well using the calculated results previously obtained by Matsuo and Sasyo (1981,a).

Discrimination of Solid from Liquid Precipitation over Northern Eurasia Using Surface Atmospheric Conditions*

“…In general, the higher CTs are found at stations with lower relative humidity and lower CT stations are associated with higher relative humidity. This is consistent with other studies that suggest snow is more likely to occur at higher air temperature conditions when the air is dry (Matsuo et al 1981;Motoyama 1990). The correlation coefficient between the two is 20.4087 (sample size of 547 stations), which is statistically significant at the 99% level and above.…”

“…In addition to air temperature, other variables that can influence precipitation types include humidity, because of its evaporating role in cooling (Matsuo et al 1981;Motoyama 1990); air density/pressure that affects the falling speed of each snow flake (Stull 2000; U.S. Army Corps of Engineers 1956); salt content in droplets that reduce freezing point (Dai 2008); elevation that affects the thickness of the air layer through which a snow flake travels; and topography that influences direct solar heating of the ground. Most of these factors are not dominant ones, but they do influence CT values to varying extents and with varying degrees of complexity.…”

“…Dewpoint temperature is directly related to atmospheric humidity, the second-most significant factor in determining precipitation type (Matsuo et al 1981), and it may have a more consistent critical value for mountain stations (Marks and Winstral 2007). The winter season is excluded from this study because of the fact that liquid precipitation events are mostly limited to European Russia; the rest of the region is predominantly solid precipitation during winter (Ye et al 2008).…”

Freezing rain and sleet climatology of the southeastern USA

“…It has been well documented that hydrometeor phase changes, both aloft and at the surface, can warm or cool ambient temperature depending on the local conditions, or can lead to a persistence of a O°C temperature (Stewart & Yiu 1993). The precipitation progression can often be complex, oscillating from snow to rain to snow with intermixed FR and S1 (Stewart & Patenaude 1988) Table 1) precipitation rates are associated with S1, while lower DATA precipitation rates are found with FR (Matsuo et al 1981). Relative humidity also affects the observed pre-…”

“…The meteorological data used in the investigation is cipitation type (through evaporation and condensathe TD-3280 Surface Airways Observation dataset tion) with higher relative humidities leading to more (NCDC 1991) for 44 stations across the southeastern FR, and vice versa (Matsuo et al 1981).…”