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Guide to TahoeClim Data and Tools

Some of the tools available on TahoeClim and a brief look at climate trends in the Tahoe Basin.

Jump to sources and tools for acquiring/visualizing daily or monthly temperature and precipitation only

Jump to sources and tools for acquiring/visualizing sub-daily, daily, or monthly data for a variety of variables

Daily and monthly temperature and precipitation resources

Station data

The best option for climate data representative of a point location in the Tahoe area is to use data from a station. Available stations are shown on the TahoeClim map.

The images above show climate data for the NWS Cooperative observer station at Tahoe City. The image on the left shows average and extreme maximum and minimum daily temperatures for the station’s period of record (through March 2013). The image on the right shows average daily snow depth at the station for its period of record. These graphs and others as well as raw and summarized data for the station are available for COOP and other stations by clicking on their markers on the TahoeClim map.

Monthly Gridded Data and Tools

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To look at averages of climate variables over large areas or estimate values for a location where no station exists, there are several gridded data sets and visualization tools available and described below. These tools should be used with care and caution as they are performing interpolations to a location or extrapolations over an area so may not display the same values as a station located at the point of interest. These tools provide a “best guess” of conditions at a location or over an area.

The upward trends in temperature in the Sierra Nevada and Tahoe Basin have been most apparent in minimum temperatures than maximum or average temperatures. The California Climate Tracker tool uses PRISM data and can be used to look at approximations of temperature departures from average and precipitation totals for the state of CA or by region from 1895-precent (2013 shown here).

Looking at the Sierra region, December-January-February minimum temperatures show a tendency to be warmer than normal over the last 20-30 years, while the maximum temperature shows no discernable trend.

June-July-August minimum temperatures in the Sierra show an even stronger trend towards warmer than average over the last 20 years according to PRISM data using the CA Climate tracker tool. Maximum temperatures again show no discernable trend.

The Climate tracker can also be used to look at precipitation trends for regions of California 1895-present. Both December-January-February precipitation and water year (October 1-September 30) display variable precipitation amounts.

To zero in on the Tahoe area, the Westmap for Tahoe tool is useful. Westmap uses the same PRISM dataset as the California Climate tracker and can be used to look at any PRISM grid point in the western US. For Tahoe, we have created three regions: the Lake itself, the hydrologic basin, and a larger region surrounding both. Westmap for Tahoe has temperature and precipitation variables.

Over the Tahoe Basin, both winter (DJF) precipitation (left) and water year precipitation (right) vary greatly from year-to-year, similar to the Sierra region. Max, min, and average temperature graphs can also be produced for the three defined Tahoe regions at Westmap for Tahoe

Freezing level is important in determining whether precipitation in the Sierra will fall as rain or snow and the rate at which snowpack will melt. The North American Freezing Level Tracker tool estimates freezing level height at a point using the NCEP/NCAR Global Reanalysis dataset. Reanalysis data is produced from 1948-present using satellite and radiosonde data. The horizontal baseline indicates the mean freezing level for the period of record. Red indicates freezing levels higher than average and blue indicates below average.

The images shown here are for a point near the center of the Lake Tahoe Basin. Winter (DJF) freezing level shows some tendency towards higher freezing level in the last 20-30 years. Spring (MAM) shows a trend toward much higher freezing levels since the late 80’s, which can impact timing of snow melt and water resources. The Freezing Level Tracker can be customized to your location of interest for four different temperature levels.

Sub-daily Data and Tools for Many Variables

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Many station networks record several meteorological variables in addition to temperature and precipitation. These include Snotel, RAWS, Desert Research Institute, NDOT, Airports, UC Davis Remote, and Reno-Carson Network. You can obtain data for these stations and produce graphs stations by clicking on their markers on the Tahoeclim map.

This example shows wind speed and direction distribution in May at Slide Mountain, Nevada over the station’s period of record. During the daytime the wind blows from the southwest approximately 50% of the time. About 12% of the time, it is out of the north. During the night, wind from the southwest still dominates, though winds are also out of the west 12% of the time and out of the north 13% of the time.

This graph shows solar radiation for 10 days at a RAWS station in Little Valley, Nevada. The solar radiation graph can be used to determine if clouds were present, which causes less radiation to be received at the station. RAWS and other stations with solar radiation data can be found using the station finder on the Tahoeclim map.

Spatial images of 13 meteorological variables at 7 pressure levels are available for the Tahoe Basin at 4-km resolution from the archive of CANSAC WRF/MM5 weather forecast model outputs. The raw data is also available to download. More information about the CANSAC MM5 and WRF model are available on the CANSAC homepage.

The left image shows 750 mb (approximately 8000 ft) temperatures over the Tahoe Basin on May 10, 2013 at ???. The image on the right shows winds over the Basin at the same time. Current forecast maps using the WRF model at 2 km resolution are available by going to the CANSAC WRF model output page.

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