U of M GEOG 5426 - INTRODUCTION TO THE NCEP - NCAR REANALYSIS (2 pages)

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INTRODUCTION TO THE NCEP - NCAR REANALYSIS



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GEOG5426 CLIMATE VARIATIONS EXERCISE 1 INTRODUCTION TO THE NCEP NCAR REANALYSIS Composites and anomalies Question 1 Geopotential height is one of the primary variables used to describe the state and structure of the atmosphere In a short paragraph provide the de nition for geopotential height and explain brie y how it can be useful in climatological analysis Question 2 I ve created three maps that illustrate the di erent perspectives that we use to examine the behavior of a climatological eld like geopotential height The rst map a above left shows mean geopotential height across North America during winter December to February calculated over the period 1949 to 2011 The second map b upper right plots the same variable during a single year 2011 and the third c below right shows the anomaly for that month In a short paragraph describe the main features shown on these maps and explain how each of these views long term mean singleyear average or single year anomaly help us understand the structure of the atmosphere Question 3 Visit the page on Monthly Seasonal Climate Composites at http www esrl noaa gov psd cgi bin data composites printpage pl First create a map showing sea surface temperature anomalies use the variable NOAA OI SST for the period December to February for the following years 1982 83 1993 94 1994 95 and 1997 98 Describe the spatial patterns present in the anomaly map and their magnitudes What feature of the climate system is most prominent in your map Second create another anomaly map for the same set of years this time plotting the Palmer Drought Severity Index PDSI The PDSI which estimates local drought conditions using a simple model of soil moisture maps both unusually wet large positive numbers and unusually dry large negative numbers conditions What is the spatial pattern of drought that is associated with anomalous sea surface temperatures Finally repeat the rst and second parts of this question using a di erent set of years 1988 89 1998 99 and answer the same questions Question 4 One alternative to mapping climate variables is to create plots that average conditions across lines of either latitude or longitude Plot mean zonal winds for January and July 2011 by latitude showing both the Northern and Southern Hemispheres What is the main component of the climate system that is visible in these maps and why does it change between the two seasons particularly in the Northern Hemisphere Correlation and regression Question 5 Visit the page Linear Correlations in Atmospheric Seasonal Monthly Averages at http www esrl noaa gov psd data correlation Correlate the time series for the North Atlantic Oscillation NAO with sea level pressure during winter December to February First plot the result using a map showing the entire Earth Plot Region Type ALL and then repeat for only the Northern Hemisphere Plot Region Type Northern Hemisphere Describe the major features of the second map Repeat the analysis using regression instead of correlation How has your map changed Why do you think regression produces a somewhat di erent set of spatial patterns Question 6 Regress Nino 3 4 against winter surface temperature Your map should illustrate the regression pattern across all of North America don t show only the United States First explain what the Nino 3 4 index physically represents Next describe the pattern and magnitude of response exhibited by North American temperatures to the El Nino Southern Oscillation Question 7 Describe brie y the di erence between correlation and regression Explain why you might use one tool over the other when comparing a time series to a climatological eld Plot time series Question 8 Visit the page Create a monthly seasonal mean time series from the NCEP Reanalysis Dataset at http www esrl noaa gov psd cgi bin data timeseries timeseries1 pl Plot the time series for average annual January to December air temperature for the region around the Twin Cities What are the warmest and coldest years in this record Due at the beginning of class on March 7


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