| | Precipitation | Soil moisture | Data sources | Explanation of terms
.
Summary
Since the last report (May 31, 2008) significant precipitation was received through most of the reporting area, providing moisture needed for crops and improving soil moisture reserves. However, through parts of the Central and Southern Regions, high and very high precipitation accumulations combined with the moderately low to low temperatures resulted in localized wet areas, on poorly drained lands. The south-western parts of the Peace Region, where precipitation accumulations are in the moderately low-to-low range, are currently the driest portions of the reporting area.
Since the last report, precipitation in excess of 50 mm was recorded across much of the Southern and Central Region, the southern and northern parts of the Northern Region as well as the central parts of the Peace Region. The rest of the reporting area recorded precipitation in the range of 20-50 mm with the exception of isolated pockets, with less than 20 mm, located in the Northern Region as well as in the south-western parts of the Peace Region. Some of the stations in the southern foothills and mountains, record in excess of 140 mm.
Average daily mean temperature, relative to long term normal, in the reporting areas, during the past 15 days, varied from near normal to moderately low across most of the northern and the Peace Regions, as well as the western part of the central and Southern regions. The rest of the reporting area recorded low to very low average daily mean temperatures, which likely slowed down crop growth (Figure 6).
Growing season precipitation accumulations to date (April 1 to June 22, 2008) relative to the long term normal, are at least near normal across the reporting area, with the exception of few isolated pockets with moderately low accumulations located in the Northern and Central Regions. Moreover, in the Peace Region, a pocket in the north and an extended area in the south-western part, recorded moderately low and low accumulations. Conversely, an extended area in the western and south-western part of the Central Region extending into the Southern Region, along with isolated pockets in the eastern part of the Southern Region, have received high to extremely high accumulations, resulting in wet conditions.
Currently, large parts of the plains reporting areas have soil moisture levels well above 75 mm with the exceptions of an extended corridor, with soil moisture levels in a range of 25 to 75 mm, that stretches from the eastern part of the Central Region to the western part of the Northern Region. In the Peace Region, soil moisture levels in the central and eastern parts was in the 75 to 100 mm range grading down to 25 to 75 mm range, in the southwest and the north-eastern corners of the region. Comparatively, soil moisture reserves relative to long term normal are at least near normal over most of the plain areas, with the exception of few pockets and an extended area in the western part of the Northern Region with low to moderately low soil moisture reserves. In the Peace Region soil moisture reserves relative to long term normal graded from above near normal accumulation in the central part of the region to low and very low accumulations both in the south-western and north-eastern part of the Peace Region.
A large selection of related maps can be found at http://www.agric.gov.ab.ca/acis, under the Quick Viewer tab.
Precipitation
Precipitation since the May 31, 2008 Drought Report (Figure 1)
Since the last report, precipitations in excess of 50 mm were recorded across much of the Southern and Central Region, the southern and northern part of the Northern Regions as well as the central parts of the Peace Region. The rest of the reporting area recorded precipitation in the range of 20-50 mm, with the exception of isolated pockets in the Northern Region and in the south-western parts of the Peace Region, where less than 20 mm was recorded. Some of the southern foothills and mountains stations record more that 140 mm.
Peace Region: Precipitation accumulations across the central, north-central and the eastern border of the region ranged from 50 to 70 mm. The rest of the region recorded less than 50 mm, with the south-western portions receiving the least precipitation (less than 20 mm). Precipitation accumulations in the region were greatest at the Jean Cote AGCM station (71.2 mm) followed by the Peace River A station (68.2 mm), both located in the east central parts of the region. The lowest accumulation was recorded at Cleardale AGDM station (9.8 mm), followed by Rycroft AGCM station (10.9 mm) and Fairview AGDM station (14.8) all located in the south-western portions of the region.
Northern Region: Precipitation accumulations in most of the western and central parts of the region and a pocket in the eastern border of the region were in the range of 25 to 50 mm, including two isolated pockets with less than 20 mm. The rest of the region recorded precipitation varying within the 40 to 78 mm range, with the exception of few isolated and scattered pockets in the range of 80 to 110 mm. The highest precipitation was recorded at Smoky Lake AGDM station (109.3 mm), in the north central parts, followed by the Holden AGCM station (91.1 mm) in southern part of the region. The lowest amount was recorded in Busby AGCM station (13.1 mm) followed by Tulliby Lake AGCM station (19.5 mm) located in the central and the eastern parts of the region, respectively.
Central Region: In general, precipitation accumulations across the region graded from 100 to 150 mm across the west to 60 to 100 mm across most of the central and the eastern parts of the region, with the exception of two isolated pockets, in a 30 to 50 mm range. The highest precipitation was recorded at the Sundre A station (148.2 mm) followed by the Water Valley station (137 mm), both located in the western part of the region while the lowest was recorded at the Hemaruka AGCM station (34.8 mm) in the east followed by Battle River Headwaters station (34.4 mm) in the northwest.
Southern Region: Precipitation accumulations across the region graded from well above 140 mm in the south-west and above 100 mm in the north-western parts of the region to lows of 50 to 60 mm in pockets scattered across most of the north central, eastern and south eastern parts of the region, with the exception of two pockets in the 30 to 40 mm range found in the southeast corner and some areas in the 90 to 100 mm range found in the eastern part of the region. The greatest accumulations were recorded at the Chief Customs station (209 mm), followed by the Spionkop Creek station (179.1 mm), both located in the south-western foothills and mountains. The lowest accumulations in the region were recorded at the Onefour CDA stations (34.2mm) followed by the Manyberries AGCM (48.6 mm) in the south-eastern parts of the region.
Growing Season Precipitation Accumulations Relative to Long Term Normal (1961-2005) (Figure 2)
Growing season precipitation accumulations relative to long term normal to date, (April 1 to June 22, 2008) were at least near normal across most of the reporting area, with the exception of few small scattered pockets classified as having moderately low accumulations located in the Northern and Central Regions and an extended area with moderately low to low accumulations found in the south-western parts of the Peace Region as well as a pocket of moderately low in the northern part of the Peace Region.
Peace Region: To date, growing season precipitation is at least near normal across most of the region with the exception of an extended area in the southwest with moderately low and low accumulation and a pocket in the north with moderately low accumulations.
Northern Region: Most of the region has received at least near normal growing season precipitation to date, with the exception of a few, small isolated pockets with moderately low accumulations, scatted across the region
Central Region: Growing season precipitation relative to long term normal was the highest in the reporting area, with much of the south-western and central parts of the region reporting at least high accumulations, grading to near normal accumulations across the northern and eastern parts of the region including two isolated pockets with moderately low accumulations.
Southern Region: In general, growing season precipitation accumulation relative to long term normal in the region ranged from a very high and high in the northwest, north, and also in few pockets in the centre and eastern parts of the region, to near normal in a few pockets scattered throughout the region.
Average Precipitation Accumulations for July (Figure 3)
July marks the beginning of a drying trend in the Southern Region, but remains one of the wettest months in the year (similar to June) across the rest of the reporting area. Historically, the first half of July is typically wetter than the last half. For July, precipitation ranges from 30 to 40 mm in the southeast, to greater than 100 mm across the western parts of the Northern Region and south-eastern parts of the Peace Region.
Soil Moisture in the Agricultural Regions of Alberta (Figure 4 and Figure 5)
To date, large portions of the plains reporting area have soil moisture levels well above 75 mm, with the exception of an extended corridor in the 25 to 75 mm range, stretching from the eastern parts of the Central Region to the western parts of the Northern Region. In the Peace Region, soil moisture reserves graded from the 75 to 125 mm range in the central parts, to 25 to 75 mm in the south-western and north-eastern corners of the region. Moreover, modeled soil moisture reserves relative to long term normal are at least near normal over most of the plains reporting areas, with the exception of few pockets and an extended area in the western part of the Northern Region, with low to moderately low soil moisture reserves. In the Peace Region modeled soil moisture reserves relative to long term normal graded from above near normal accumulations, in the central parts of the region to low and very low accumulations to the south-western and north-eastern part of the Peace Region.
Peace Region: In the central part of the region, soil moisture levels were in the 75 to 125 mm range and graded to 25 to 75 mm in the south-western and in north-eastern parts of the region. Similarly, modeled soil moisture reserve relative to long term normal graded from above near normal, in the central parts of the region, to low and very low accumulations in the south-western and in north-eastern parts of the region.
Northern Region: Generally, soil moisture levels were in the 75 to 125 mm range in the west, north and the eastern parts of the region and then grade down to the 50 to 75 mm a range corridor in the centre, which extends to the south-eastern part of the region, including pockets in the 25 to 50 mm range. Modeled soil moisture reserves relative to long term normal were at least near normal across much of the region with the exceptions of moderately low and low accumulations in the western parts of the region.
Central Region: Soil moisture levels in the region graded from more than 125 mm in the west, down to the 50 to 75 mm range in the east with some pockets in the 25 to 50 mm range. Modeled soil moisture reserves in the western and along the southern border of the region varied from high to very high, grading to near normal, in the northern parts of the region.
Southern Region: In general, soil moisture levels in the region graded from more that 125 mm in the west to the 75 to 100 mm range in the east, with the exception of the east where one pocket in the 100 to 125 range can be found along with two pockets in the 50 to 75 range. Modeled soil moisture reserves relative to long term normal graded from high and very high along the northern border of the region to moderately high in the south and to a near normal in the western parts of the region.
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 normals.
Explanation of Terms
Precipitation Accumulations - Frequency of Occurrence
Precipitation accumulations, 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 1st
- Cold Season to date- Starting October 1st
Selected maps from this series are included in this report.
Precipitation accumulations for each period are then determined by ranking the precipitation accumulations during similar periods 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 accumulations 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 June 27, 2008.
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 May 31, 2008 |
|