| NATS 101 Lecture 19 Monsoons |
| Review Land-Sea Breeze (Courtesy of Mohan Ramamurthy, WW2010) |
| Review: Mountain-Valley Breeze |
| Thermally Direct Circulation |
| Monsoon |
| Seasonal Reversal of Prevailing Wind | |
| Wind shift often accompanied by | |
| Major Change in Weather | |
| Summer Rains - Often Abrupt Onset | |
| Winter Dryness | |
| Major Monsoon occurs over Asia | |
| Weaker Monsoon occurs in North America |
| Monsoon |
| Land mass is colder than ocean in winter | |
| Land-sea temp contrast reverses in summer | |
| Wind forced by seasonal changes in PGF Higher SLP over land in winter FOffshore flow at Surface | |
| Lower SLP over land in summer FOnshore flow at Surface |
| Monsoon |
| Onshore flow leads to surface convergence | |
| FRising motion over land during summer | |
| Offshore flow leads to surface divergence | |
| FSinking motion over land during winter | |
| Monsoon is Thermally Direct Circulation | |
| FWarm Air Rises - Cold Air Sinks |
| Slide 8 |
| Slide 9 |
| Asian Winter |
| Asian Summer |
| Monthly Average Rain Cherrapunji |
| January |
| July |
| Geography of Region |
| Terrain |
| Terrain (300 m) | |
| Steep slopes of Sierra Madre Occidental | |
| Warm Waters |
| Monthly Rainfall |
| Mexican Monsoon | |
| Similar onset | |
| Similar behavior butÉ | |
| Much less intense | |
| A Wimp Compared to Asian Monsoon |
| Percentage of Annual Rainfall |
| Accounts for up to 70% total rain in monsoon core | |
| Tucson ~50% | |
| Phoenix ~40% |
| July minus June Rainfall |
| Monsoon Evolution from Satellite |
| CCT < -38oC Frequency | |
| Centered over W. Mexico | |
| June start over Mexico | |
| AZ at northern fringes of heart of monsoon | |
| Rains reach SE Arizona by July |
| June-July 500 mb Flow |
| May 500 mb Flow |
| July 500 mb Flow |
| Monthly Winds and RH (Guaymas, Sonora) |
| July 900 mb Flow |
| Diurnal Winds 450 m AGL |
| Summary |
| Monsoons | |
| Differential Heating Between Land and Oceans | |
| Seasonal Reversal of Wind | |
| Summer Rain - Winter Aridity | |
| Thermally-Direct Circulation | |
| Regions | |
| Major Monsoon Occurs over SE Asia | |
| Weaker Monsoon Occurs over North America | |
| Africa, Australia, South America in SH |
| Assignment |
| Topic- Global Scale Winds | |
| General Circulation | |
| Reading - Ahrens 181-189, 343-349 | |
| Problems - 7.11, 7.12, 7.13 | |