Answers to Analyzing Data 2.1 Questions
1. Greater solar radiation would be absorbed by the dark green crops. Given incoming radiation of 470 W/m2, light-colored grasses reflect 122 W/m2 (26% of 470) and absorb 345 W/m2.
With irrigated crops, 85 W/m2 (18% of 470) is reflected and 385 W/m2 is absorbed. Thus, with approximately 40 W/m2 greater heat absorption, the change in albedo alone would result in warming.2. The greater surface roughness of the crop plants would cause greater heat loss (approximately 40 W/m2) due to convective transport of pockets of warm air from the surface to the upper atmosphere.
3. Higher leaf area coupled with greater soil moisture in the irrigated crop system would result in higher evapotranspiration. As a result, more heat is lost from the surface to the atmosphere via latent heat flux by the irrigated cropland relative to the short-grass steppe.
4. The total difference in heat lost associated with the land use change from grassland to irrigated crop is 60 W/m2 - 40 W/m2 = 20 W/m2. The greater total heat loss by the irrigated crop relative to the short-grass steppe would result in cooler temperatures.