This map explores the historical probability of seasonal weather-within-climate temperature characteristics given the state of ENSO.
This map shows the historical probability of seasonal weather-within-climate temperature characteristics falling within the upper (High), middle (normal), or bottom (Low) one-third ("tercile") of the 1961-2020 historical distribution in Lesotho given the state of ENSO (El Niño, Neutral, La Niña) during that same season.
Here, the ENSO state for each season is defined according to the Oceanic Niño Index (ONI). It is calculated using Sea Surface Temperature (SST) anomalies, based on centered 30-year base periods updated every 5 years, in the geographical box (170˚W, 5˚S, 120˚W, 5˚N). A season is considered El Niño (La Niña) if it is part of at least 5 consecutive overlapping 3-month long seasons where the ONI is above 0.5˚C (below -0.5˚C). Use the controls on the page to select the season, temperature tercile category of interest, and ENSO state. The analysis reproduces, using same SST dataset, the following definition from NOAA.
Clicking on the map will then display, for the selected point, yearly seasonal temperature weather-within-climate time series. The color of the bars depict what ENSO phase it was that year, and the horizontal lines show the historical terciles limits. This allows to quickly picture what years fell into what ENSO Phase and into what Temperature Tercile category.
The analysis can also be done on temperature averaged over Lesotho's Provinces and councils administrative boundaries. Use the menu in the top Control Bar to choose at which spatial level you wish to work, then, to select an area, you can either click on the map (layers of the contours of the different administrative levels can be activated for visualization in the Layers control of the map); or select a name in the drop down menu generated accordingly to the spatial level selected. Note that this drop down menu lists only names of areas that are currently in view on the map. Note also that in the case of 2nd level of administration, if the list is too long, it won't show up or update: zoom over the map to make the list shorter.
NB: This is not a forecast. It is based on historical observations of temperature and SST. However, it would be a good tool for exploring the effect of different ENSO phases on seasonal temperature.
Reference for ENSO phases definition: V. E. Kousky and R. W. Higgins, 2007: An Alert Classification System for Monitoring and Assessing the ENSO Cycle. Wea. Forecasting, 22, 353–371. doi: http://dx.doi.org/10.1175/WAF987.1
Years and Season: Specify the range of years over which to perform the analysis, and choose the start
and end dates of the season over which the diagnostics are to be performed.
Hot/Cold Day Definition: This threshold is used to define in Celsius degrees (non inclusive) the temperature
under which a day is considered cold if the mean temperature is below it; or the temperature
above which a days is considered hot if the mean temperature is above it; or the reference
temperature to compute the growing/chilling degree days.
Seasonal daily statistics: Choose the seasonal diagnostic quantity (i.e the statistic of the daily data) to
be computed for each season, from the following choices.
Growing/Chilling Degree Days: Growing or chilling degree days are summations of positive/negative differences
between the mean daily temperature and user-defined reference base temperature during
the season. They are comparable to the more familiar cooling/heating degree day definitions
utilized by energy-sector.
Number of Cold and Hot days: The number of cold or hot days during the season according to the user-defined threshold
and according to the mean daily temperature.
Spatial Resolution: The analysis is performed and mapped at each grid point.
Data Source: Reconstructed temperature data over land areas on a 0.0375˚ x 0.0375˚ lat/lon grid (about 4 km of resolution). Minimum and maximum temperature time series (1961 to 2020) were generated by combining quality-controlled station observations with downscaled reanalysis product.
Data Source: Sea Surface Temperature : Extended Reconstructed Sea Surface Temperatures (ERSST), at 2˚ spatial resolution, produced by NOAA CDC.
Contact help@iri.columbia.edu with any technical questions or problems with this Map Room.