DJF Visualizations

Tim Scheitlin, 9/22/2000 Hi Folks,

Based on ideas and suggestions for visualizing some of the subtle aspects of an El Nino signal from Rajul's earlier work , I have reprocessed the NCEP (atmosphere) and Gent (ocean) data to create a new set of visualizations using data from only the Dec-Jan-Feb time periods (when El Nino typically peaks). The data was then further divided into El Nino, Normal, and La Nina categories to allow for comparisons between these events.

La Niña:1950, 1956, 1971, 1974, 1976, 1989, 1999
El Niño: 1966, 1978, 1983, 1987, 1992, 1998
Normal: 1957, 1961, 1972, 1979, 1984, 1985, 1986, 1990, 1996, 1997

Walker Cycle

Averaging the DJF data over a set of El Nino, Normal, or La Nina years results in a single timestep. Therefore, to generate a trajectory animation, the UVW wind data were duplicated 100 times and then used to calculate the trajectory path over 100 timesteps as shown in the following animation. This single trajectory clearly shows the clockwise circulation associated with the Walker Cycle at the Equator over the Pacific.

movie loop: mpeg quicktime
This movie shows a single wind trajectory path over the equatorial Pacific during DJF normal years. The colored plane at the bottom represents the convective precipitation rate.

This next set of stills shows the East-West (U) and Vertical (W) wind components. If we focus over the Pacific region in each of the images, the East-West visualizations show east to west circulation (blue) at the lower levels and west to east circulation (red) at the higher levels. In the Vertical wind visualization, during normal years, there is upward circulation (red) in the Western Pacific and downward (blue) circulation in the Eastern Pacific.

El Nino Years Normal Years La Nina Years Description

East-West (U) wind component with vectors at the Equator (1000-100mb).

Surface East-West (U) wind component with vectors.

200 mb East-West (U) wind component with vectors.

Vertical (W) wind component with vectors at the Equator (1000-100mb).

Hadley Cell

Visualizing the Hadley cells is a little more difficult, and, IMO, the results are not as obvious. Maybe averaging the data over several latitudes would bring out these features more clearly?

These next two animations show a longitudinal slice plane as it is passed from west to east in a static data set of normal year DJF averages.

Normal Years Description

movie loop: mpeg, quicktime

Vertical (W) component of the wind field. Red up, blue down.

movie loop: mpeg, quicktime
North-South (V) component of the wind field. Red north, blue south.

El Nino Years Normal Years La Nina Years Description

North-South (V) wind component at 190 east longitude (1000-100mb).

North-South (V) wind component at surface.

Vertical (W) wind component at 190 east longitude. Red/up, blue/down.

Anomaly Fields

The following visualizations were created by subtracting the Normal data from the El Nino or La Nina data to create a difference/anomaly field.

El Nino Years	La Nina Years	Description
		Anomaly field for the Convective Precipitation Rate. (red -, blue +)
		Anomaly field for Precipitable Water. (red -, blue +)

Atmospheric Data Description

Dimensions : 73x144x12
Variables include each of the following DJF averages for El Nino, La Nina, and Normal years:

UVW wind components (U,V,W)
Pressure (Press)
Precipitable Water (PWAT)
Temperature (TEMP)
Relative Humidity (RH)
Convective Precipitation Rate (CPRAT)
Total Cloud Cover (TCDC)

Data Source: NCAR MSS Archives NCEP Reanalysis Atmospheric Data.

Vis5D data: DJFatmos1.v5d (7.6 MB, 1 timestep)
Vis5D data: DJFatmos100.v5d (757 MB, 100 timesteps) useful only for generating trajectories.

Ocean Data

Nothing much new to show here. The same features as seen in previous work are still evident.

El Nino Years	La Nina Years	Description
		Sea Surface Temperature Anomaly fields.

El Nino Years	Normal Years	La Nina Years	Description
			Thermocline from 0 to -232m. at equator

Ocean Data Description

Dimensions: 30x90x15 ranging from 30 N. Lat to 30 S. Lat, 60 W. Lon to 240 W. Lon, 0-232 meters below sea level

Variables include each of the following DJF averages for El Nino, La Nina, and Normal years:

Temperature (T)
Temperature Anomalies (Tanom)
U,V,W components of the ocean current (U,V,W)

Data Source: Dr. Peter Gent (NCAR Climate and Global Dynamics Division) generated from the ocean component of the Climate System Model.

Vis5D Data: sDJFocean1.v5d (2.4 MB, 1 timestep)

Normal Years	Description
	movie loop: mpeg, quicktime Vertical (W) component of the wind field. Red up, blue down.
	movie loop: mpeg, quicktime North-South (V) component of the wind field. Red north, blue south.