Using Airborne Lidar Data to Characterize Local Surface Features and Their Influence on Wind Observations

Small scale surface features can have profound effects on wind observations. These features are poorly resolved or unresolvable by numerical weather models and can result in large biases when verifying forecasts. To understand and mitigate the impact of these features it is essential to characterize the local environment around weather observations. However, information about the area surrounding weather stations is sparse and lacking. Satellite photography lacks accurate measurements of size and height, while direct site surveys are rare and only provide information in the immediate area. Airborne lidar presents a unique opportunity to visualize a high resolution three dimensional environment around an observation site.

The New York State Mesonet (NYSM) and ASOS are two networks present in New York State (NYS) that provide high quality but vastly different wind observations. NYSM contains 126 stations that are sited across NYS and aim to provide observations in previously sparse regions. Due to a number of limitations associated with New York geography these stations are not always located for ideal wind observations. Alternatively, ASOS stations are frequently sited at airports with long unobstructed fetches. Airborne lidar scans surrounding both networks are used to recreate and characterize their local environments. These environments are compared using terrain and obstacle obstruction angle with respect to anemometer location on a network and station pair basis. Obstructions are found to be far more prominent, in both frequency and angle amplitude, surrounding NYSM stations than ASOS. These more pronounced obstructions are correlated with the on average 24% slower mean wind speeds and higher gust factors (GFs) at NYSM stations than ASOS.