Simulation of meteorological variations 



Norman Lord*t The Center for the Environment and Man 



Joseph Pandolfo The Center for the Environment and Man 



Marshal Atwatert The Center for the Environment and Man 



This study aim§ to model numerically the spatial and temporal variations in the meteorological 

 properties of the coastal tundra ecosystem. A first-phase goal is to determine the most in:4)ortant 

 natural variations of the weather and how these would probably be modified by artificial perturbation 

 of the vegetative covers. 



Originally, four terrain units were to be simulated: ridg6 and slope, lowland polygonal ground, 

 meadows, and thaw lakes. It was hypothesized that each type would be broad enough to permit its 

 local variation to be represented in terms of dependence on a vertical coordinate ranging from the 

 permafrost boundary to the upper atmosphere. Details of this project were contained in the original 

 proposal. The following is a summary of initial results. 



Of the four categories of environment comprising the entire abiotic ambience of the tundra bio. 

 sphere, lowland polygonal ground most closely corresponds to the simplifying assumptions of the 

 boundary-layer model being used to simulate the ambient physical variations. The Center for the 

 Environment and Man sea-air model was therefore modified to fit this case first and applied to a 

 time interval for the Barrow area that were available from the University of Washingt-on, July 1966 data. 



The boundary layer model, modified for soil and air, starts from initial values and predicts 

 primarily the variations in the following physical characteristics observable for a period of several 

 days: 



1) Wind-height profile 



2) Temperature-height profile in air and extending below ground surface 



3) Moisture-height profile in air but ending at ground surface 



4) Vertical component of energy flux at ground surface and at a lower reference level. 



As part of the boundary conditions, the reflectivity to solar radiation (i.e. albedo), thermal 

 conductivity below the surface, and a constant temperature at a carefully chosen reference depth 

 must be specified. Existing soil temperatures showed a fairly constant temperature at the 16-cm 

 depth and a rough judgement was made so that at 20 cm below the surface, temperatures would be 

 constant at 274. 5°K. Since both albedo and thermal conductivity were not directly measured in 

 1966, the principal interest in applying the model was to find the particular albedo and thermal con- 

 ductivity which produce simulated results in agreement with those observations. If such albedo and 

 thermal conductivity conformed approximately to values derived from 1970 field and laboratory obser- 

 vations, the model might then be applied with confidence to a wide variety of situations. Of 

 particular interest would be disturbances leading to changes in vegetation. 



Initial profiles of wind, temperature, and moisture were derived from monthly average data 

 collected by the World Meteorological Organization for Point Barrow, Alaska, July 1966. Subsurface 

 monthly average temperatures were derived from 1966 data. Then, keeping their profiles constant, 

 a matrix of different albedo and assumed depth, invariant thermal conductivities were specified for 

 a set of 22 experiments. The range of thermal conductivity was judged by a rough measure of phase 

 lag in the estimated diurnal component of temperature variation between surface and the 16-cm 

 depth. 



Results of the numerical experiments are given in Table XI wherein thermal conductivities are 

 stated in cgs units, temperatures in degrees Kelvin, and time lags in units of 5 minutes. These data 

 may now be compared with their counterparts in the 1966 data base which may be stated as follows: 



♦Principal author. 



tNot at Barrow during 1970. 26 



