| | Precipitation | Snow pack | Data sources | Explanation of data
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Summary
Since the last drought report (November 30, 2008) significant precipitation (20 to 40 mm) has fallen over much of the Peace Region, the northern and central parts of the Northern Region, the western parts of the Central Region, and over most of the Southern Region. Precipitation was general below 20 mm across the eastern-half of the central region, as well as in much of the southern parts of the Northern Region. The greatest amounts were received across the southern foothills, where precipitation ranged from 40 to 120 mm.
Average daily mean temperatures during the past 15 days, relative to the long-term-normal, across the Peace Region, most of the eastern halves of the Northern and Central Regions, as well as the north central and south-eastern corner of the Southern Region were low. The rest of the reporting area recorded at least near normal average daily temperature regimes (Figure 6).
Cold Season precipitation (Oct 1 to March 31) accumulations relative to long term normal, to date, are extremely low to low across the south-eastern parts of the northern region and the northern parts of the Central region. In general, much of the Northern and Central region have received at least moderately low cold season accumulations, with many areas grading to low or worse. Elsewhere, accumulations were at least near normal across most of the Peace Region and extreme northern parts of the North Region, and in few pockets in the Central Region and across most parts of the Southern Region.
Modeled snow pack accumulations relative to long term normal for this time of year across are at least near normal across the Peace Region, the northern parts of the Northern Region, the southwestern and eastern corner of the Central Region, and over much of the Southern Region. Elsewhere, accumulations are moderately low with few pockets of low.
A large selection of related maps can be found at http://www.agric.gov.ab.ca/acis, under the Quick Viewer tab. Note these maps are updated once a week (usually by Wednesday) providing updates between drought reports.
Precipitation
Precipitation since the November 30, 2008 Drought Report (Figure 1)
Since the last report on November 30, 2008 significant precipitation (20 to 40 mm) was recorded over much of the Peace Region, the northern and central parts of the Northern Region, the western parts of the Central Region, and over most of the Southern Region. Precipitation in the rest of the reporting area was less than 20 mm, with the exception of the foothills, with precipitation accumulations ranging from 40 to 120 mm.
Peace Region: Precipitation accumulations across the region generally ranged from 30 to 40 mm, with lower amounts of 20 to 30 mm being recorded in the western and southeastern parts of the region. The highest precipitation accumulations were recorded at Sprit River Auto station (41.8 mm), followed by Cleardale AGDM station (33.9 mm) both located in the west, while the lowest accumulations were recorded at La Crete AGCM station (15.1 mm) in the north, followed by the Fairview AGDM station (19 mm) in the central part of the region. Since the last drought report, precipitation accumulations relative to long-term-normal were at least near normal across most of the region.
Northern Region: Precipitation accumulations graded down from 20 to 40 mm in the north and central parts of the region to 10 to 20 mm range across most other parts of the region. The highest precipitation accumulations were recorded at Dewberry AGCM station (43.2 mm) in the east, followed by Atmore AGDM station (38.5 mm) located in north, while the lowest accumulations of 7.7 mm was recorded at the Wainwright A station in the southeastern part of the region. Precipitation accumulations relative to long-term-normal were at least near normal across most parts of the region, with the exception of a few isolated pockets in the southeast, where moderately low accumulation were received.
Central Region: Precipitation accumulations graded down from 30 to 40 mm along the west to 10 to 20 mm across most of the region to the east, with the exception of a few isolated pockets that received less than 10 m. The highest precipitation accumulations were recorded at Elbow RS station (48.4 mm) in the southwest corner, followed by Rocky Mtn House A station (45.9 mm) in the northwest corner, and the lowest were recorded at Esther Station (7.3 mm) in the east, followed by Morrin AGDM (8.7 mm) station in the central part of the region. Precipitation accumulations relative to long-term-normal graded from high in the west to near normal conditions in the rest of the region.
Southern Region: Precipitation accumulations graded from above 40 mm in foothills to 20 to 30 mm across most of the region, and then down to 10 to 20 mm along the northeastern border of the region. Three scattered pockets in the 30 to 60 mm range exist in the southern and eastern parts of the region. The highest precipitation accumulations were recorded at Prairie bluff station (103.1 mm) located in the foothills, while the lowest accumulations were recorded at Brooks ASCHRC station (15.5 mm), followed by Bassano AGCM station (16.5 mm), both located in the central eastern portion of the region. Since the last drought report, precipitation accumulations relative to long-term-normal were generally moderately high across the region.
Cold Season Precipitation Accumulations relative to Long Term Normal (1961 - 2005) (Figure 2)
Cold Season precipitation (Oct 1 to March 31) accumulations relative to long term normal, to date, are extremely low to low across the south eastern parts of the Northern Region and the northern parts of the Central Region. Much of the Northern and Central Regions have received at least moderately low cold season accumulations with many areas grading to low or worse. Elsewhere, accumulations were at least near normal across most of the Peace Region and extreme northern parts of the North Region, and in few pockets in the Central Region and across most parts of the Southern Region.
Peace Region: Most of the Peace Region cold season precipitation accumulations were near normal, with the exception of three isolated pockets in the southern and northern parts of the region with moderately low accumulations.
Northern Region: Cold season precipitation accumulations in the region graded from at least near normal in the north to large pockets of very low and extremely low accumulations in the southeastern and southwestern parts of the region.
Central Region: Cold season precipitation accumulations in the region graded from very low and extremely low accumulations in the northwest and north central portions of the region to moderately low across most of other portions of the region with the exception of the southwestern and southeastern corners of the region were near normal accumulations have occurred.
Southern Region: Cold season precipitation accumulations across the region varied from at least near normal across most of the region to moderately low accumulations in a north-south band adjacent to the foothills in the west.
Average Precipitation Accumulations for January (Figure 3)
January is a typically a dry month across the reporting area, with on average about 4.9 percent of the annual precipitation falling. During this month precipitation totals range from 10 to 20 mm across most the central and Southern Regions, increasing to 30 to 40 mm in the west along the foothills. Across the Northern and Peace Regions, precipitation totals typically range between 20 to 30 mm, with the exception of the south half of the Peace Region where between 30 to 40 mm is typically recorded.
Snow pack conditions
Modeled snow pack accumulations expressed as snow water equivalent (SWE) are shown in Figure 4. Snow pack accumulations relative to long term normal are shown in Figure 5. These maps represent the current snow pack estimates in stubble fields and reflect a 30 percent precipitation loss due to blowing; in addition to losses due to sublimation and snow melt process.
Peace Region: SWE's ranged from 40 to 50 mm across most of the region with some areas estimated to have 20 to 40 mm of SWE. The snow pack accumulations relative to long term normal are generally moderately high across most of the region with the extreme parts of the northern, southwestern, and southeastern portions of the region estimated to be near normal.
Northern Region: SWE's graded from 30 to 40 mm across in the north to 10 to 20 mm across most of the region, with the exception of few isolated pockets where SWE's were estimated to be less than 10 mm. The snow pack accumulations relative to long term normal grade from low in the southeast to moderately low across the remainder of the region, with the exception of the extreme north-central and northeastern parts of the region where at least near normal accumulations are estimated to occur.
Central Region. SWE's graded from above 30 mm along the western border to a less than 10 mm across an extended area in the central and eastern portions of the region. Snow pack accumulations relative to long term normal graded from at least near normal conditions in the southwest and southeast to moderately low conditions across the rest of the region.
Southern Region: SWE's across most of the region fall in the 10 to 20 mm range with the exception of the foothill areas and an isolated pocket in the east were SWE's are estimated to be above 30 mm. The snow accumulations relative to long term normal across most of the region are at least near normal.
Data Sources:
Near Real Time Weather data
Daily and hourly near-real-time raw weather data is brought in via daily data feeds from Alberta Environment (AENV) and Environment Canada (EC). The data undergoes a preliminary computer assisted QA/QC check performed by Alberta Agriculture and Rural Development (ARD) staff. Suspicious values are checked and verified and daily missing values are filled using archived data from AENV databases or from the EC web site. If daily data is still missing, it is estimated using data from nearby stations. Maps describing current conditions are based on preliminary data that is subject to change under further review by ARD, AENV and EC.
Historical Weather data
Historical weather data was provided by Environment Canada. This data was then converted to a 10 km daily gridded weather data set that used all available daily data to generate historical climate and soil moisture normal.
Explanation of Terms
Precipitation Accumulation - Frequency of Occurrence
Precipitation accumulation, expressed as a frequency of occurrence are computed for various periods and can be found on our web site at www.agric.gov.ab.ca\acis, under the Quick Viewer tab. Maps are routinely produced for the following periods:
- Past 365-days
- Past 180-days,
- Past 90-days
- Past 30-days,
- Growing season to date -Starting April 1
- Cold Season to date- Starting October 1
Selected maps from this series are included in this report.
Precipitation accumulations for each period are then determined by ranking the precipitation accumulation during similar period dating back from 1961 to present. The current accumulation is compared to the ranked values, yielding the frequency of occurrence, based on percentiles. The percentile points were then put into arbitrary but intuitive classification fields that describe the current state as drier, near or wetter than the long term normal. The resulting map thus answers the question "how often does this occur?" The classifications are as follows:
| Description | Frequency of Occurrence |
| extremely low | drier than this, on average, less than once in 25-years |
| very low | drier than this, on average, less than once in 12-years |
| low | drier than this, on average, less than once in 6-years |
| moderately low | drier than this, on average, less than once in 3-years |
| near normal | on average, this occurs at least once in 3-years |
| moderately high | wetter than this, on average, less than once in 3-years |
| high | wetter than this, on average, less than once in 6-years |
| very high | wetter than this, on average, less than once in 12-years |
| extremely high | wetter than this, on average, less than once in 25-years |
This same scheme is then used for similar maps of soil moisture and snow pack accumulation so that comparisons can readily be made across the various map types.
Snow pack (reported during the winter season only)
Snow pack snow water equivalents (SWE) are modeled for stubble fields. SWE is defined as the equivalent depth of water (mm) that the snow pack contains if it were to be melted. SWE is computed from precipitation and subsequent losses due to blowing, sublimation and snow melt processes.
In the model, if precipitation falls when the mean daily temperature is below 2 °C that precipitation is estimated to be in the form of snow. If precipitation if estimated to fall as snow then to simulate drifting, only 70 percent of the total precipitation is allowed to accumulate resulting in a 30 percent loss due to snow "blow off". If precipitation occurs as rain on an existing snow pack, it is added directly to the snow pack as SWE.
Soil moisture (reported during the growing season months only)
Soil moisture is measured as millimetres (mm) of plant available water. Plant available water is approximately half of the total water that can be measured in the soil. Soil moisture is reported on from May through to October.
The crop gets the moisture it requires from the reserve of soil moisture, which in turn is replenished by precipitation. Soil moisture is a valuable indicator of drought potential because it indicates the reserve of water available to the crop at a given point in time. During peak growing periods, soil moisture reserves are consumed quickly and must be replenished frequently by rainfall. Poor soil moisture reserves during peak water use indicate a high risk of immediate crop stress. Prolonged stress becomes drought and results in significant unrecoverable yield loss.
Because the climate varies across Alberta, comparing current moisture levels to normal levels provides a valuable indicator of drought risk that can be applied to all localities during the frost-free season. Current soil moisture levels are compared against soil moisture levels for the same day in each year from 1961 to present. The frequency of occurrence is computed based on the percentile points, using the same method that was used for similar maps that were generated for precipitation. The frequency of occurrence is then plotted using the same class scheme as is used in the long-term (hydrologic) drought map (see table above). Soil moisture reserves with a modifier of low, indicate a need for more precipitation to restore reserves.
Soil moisture needed to return to average spring or fall conditions
Soil moisture needed to return to normal spring or fall conditions is computed by subtracting average soil moisture (spring or fall), computed using model runs dating back from 1961 from current soil moisture conditions. This yields the amount of recharge needed to bring current soil moisture levels to average. Historic model runs are then analyzed to determine how many years since 1961 that soil moisture recharge was similar to or greater than that currently needed. The number of years that this occurred is then used to compute the probability of returning to average. However, currently this process is unable to account for snow currently existing on the ground and as such is not as accurate where snow packs exist.
Report prepared by the Drought Reporting Team
Ralph Wright, Daniel Itenfisu and Isabel Simons-Everett
Alberta Agriculture and Rural Development
Edmonton, AB T6R 5T6
Contact: Ralph Wright; ph 780-427-3556
This report was created on January 8, 2009.
Drought analysis is currently scheduled at monthly intervals between October 31 and April 31, and twice monthly from May 1 to September 30. This report updates the previous report of December 1, 2008. |
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