Abstract

The North American Monsoon System (NAMS) greatly affects climate variability in the continental United States. Finding out exactly how the NAMS affects the climate will allow better prediction of future climate conditions. It is imperative that the NAMS is further researched in order to establish its climate predictability value. Precipitation and surface temperature data has been collected from weather stations all over Mexico for the years of 1990 to 2000. This data will be combined with that of the Southwest U.S., of the same time period, to be analyzed. The raw data was received in .cal and .csv format. The .cal files are converted to .csv files using an application called SuperCalc4. Using another application all of the files were converted to .asc format. A C-program was designed to scan through each file searching for missing values to be replaced and create a new file, which was in a more proper format for analysis. The data was processed using the Cressman Analysis technique so that it could be easily displayed with the GrADS graphics and display program. The information found in this research was used to support the Climate Prediction Centers (CPC) NAMS research, lead by Dr. Wayne Higgins. Dr. Higgins is finding climate patterns and characteristics to improve climate predictability. Prediction is crucial for extreme weather event safety. Better prediction gives us more warning time, which is our strongest weapon against extreme weather.

Literature Search

The North American warm season is characterized by a monsoon system often referred to as the North American monsoon system (NAMS). There is a "monsoon-like circulation regime" over the U.S. and Mexico that exerts a fundamental control on the summertime precipitation climatology of the region. Links between the summer monsoon in southwestern North America and summertime precipitation in the Great Plains of the United States may have seasonal predictive value. The evolution of the North American monsoon system follows three phases. The first of which is the development phase, that takes place in May through June, consist of a weakening northward shift of the extra-tropical storm track. Increasing frequency of occurrence of the Great Plains Low-Level Jet, east of Rockies. Increasing diurnal variability or precipitation. Mexican monsoon begins with a northward spread of heavy rains along west slope of the Sierra Madre occidental. Strengthening and northward migration of the upper tropospheric "monsoon high". The second phase of the NAMS is the mature phase, which covers July and August. In this stage the Mexican monsoon extends into Arizona and New Mexico. The upper tropospheric ridge becomes established over the west and central U.S. Warm season continental precipitation regime is established. The third and final established phase of the system is the decay phase in September and October. Mainly there is the slow weakening of the monsoon circulation system. Broadly this phase is the reverse of the development phase. The monsoon system is important to the region. It provides up to 45 percent of annual precipitation for Arizona and New Mexico, and about 60 percent of northern Mexico's rainfall, between early July and mid-September. Inter-annual fluctuations in the onset date of the monsoon in the American Southwest are significantly correlated with fluctuations in the intensity of summer rainfall in this region such that early monsoons tend to be very wet and late monsoons tend to be somewhat dry. Wet or dry monsoons in the Southwest often follow winters characterized by wet or dry conditions in the Southwest and conditions in the Pacific Northwest. Inter-annual variability of the summer monsoon in the American Southwest is modulated by decadal fluctuations in the North Pacific associated with the Pacific Decadal Oscillation (PDO). The rainfall produced by NAMS has a direct connection with sea surface temperatures. Dr. Tim Brown used satellite remote sensing to track sea surface temperatures in the northern Gulf of California, observed that the monsoon rains typically would not begin until the temperature reached and maintained at least 26° Celsius (79° Fahrenheit). The amount of precipitation that results also correlates to the gradual increase in sea surface temperatures, with the increase in rainfall in the U.S. generally following five to 15 days behind rises in sea surface temperature. Arizona and New Mexico received two-thirds of their rainfall after sea surface temperatures in the northern part of the gulf exceeded 29° C (84° F). Data from the past 26 years reinforces the relationship between rising sea temperature and increased rainfall. The features of NAMS are similar to those of other regional monsoons. Most notably the southern and east Asian monsoon complex and the Australian and West African Monsoons. While the NAMS is less impressive, it still has a tremendous impact on local climate. A monsoon system is defined as, any of a type of major wind system that seasonally reverses its direction--e.g., one that blows for approximately six months from the northeast and six months from the southwest, by Britannica. Features of the NAMS include major low-level inflow of moisture to the continent, a seasonal increase in continental precipitation and a relatively warm troposphere over the monsoon region resulting in a "monsoon high" in the upper troposphere. There are also significant regional differences that arise as a result of coastal geometry, topography and latitudinal distribution of the continents. Differential heating between land and ocean is the basic mechanism which drives monsoon circulations. There has been little research in the past on NAMS, which provides little documentation but also gives the sense of experiencing groundbreaking research. As apparent in the amount of publications on the subject, DR. Wayne Higgins is the authority on the subject and I am delighted to have to opportunity to participate in such an important research project under his guidance.

My Mentor-

My mentor is Dr. Wayne Higgins, the leading authority on the North American monsoon system. In my project there are actually three stages, in which I will be working with three different individuals. For the first step, I will start out working with Evgeney Yarosh, a contract scientist, on preparing the data. Then, I will work with Dr. Wei Shi, a research meteorologist, on analyzing the data. Finally, I will work with Dr. Wayne Higgins, who is a senior research meteorologist and will be consulting me throughout my research experience here at CPC.

My Site-

My research site was the Climate Prediction Center (CPC), located in Camp Springs, MD. CPC provides climate services to the users in government, the research community, private industry and public, both in this country and abroad. Services include operational prediction of climate variability, monitoring of the climate systems and development of databases for determining current climate anomalies and trends, and analysis and assessment of their origins and linkages to the rest of the climate systems.
The Climate Prediction Center is a division of NCEP or the National Centers for Environmental Prediction. The NCEP is the organization that prepares and makes available national forecast and outlooks of weather and climate. NCEP was created by the National Oceanic and Atmospheric Administration. The National Oceanic and Atmospheric Administration (NOAA) is dedicated to predicting and protecting the environment.