Diagnosis of winter time cold bias in the ETA and NMM models

The study of cold bias during winter time by NCEP Meso Eta and Nonhydrostatic Meso models was investigated. The cold biases usually occur during the night time when the atmosphere is usually stable. Cold biases in NMM simulation were attributed to increases in downward longwave radiation which are a result of increased cloud cover in NMM reruns. The results of NMM re-runs show that NMM shelter level cold biases at FP improved significantly in two of the chosen cold biases, and Meso Eta shelter level temperature forecasts were only slightly colder than observations in the two cases.