Length-of-Day Changes and Mountain Torque during El Nifio

Abstract

Values of mountain pressure torque are calculated for the Rocky and Andes Mountains and for the Tibetan Plateau in order to evaluate their conuibufion to the observed anomalous length-of-day (LOD) and atmospheric angular momentum (AAM) change during the period from late January to mid-February 1983. A period of rapid increase in AAM and LOD is found to coincide with unusually high values of mountain torque on the Rocky Mountains, associated with a midcontinent high-pressure event and a sequence of Pacific frontal cyclone lows hitting California. A subsequent decrease in AAM is not correlated with mountain pressure torquesover the three regions tested, thus implicating other regions or other transfer mechanisms.