Oklahoma Mesonet

1. Drought and the Modernized Cooperative Observer Network Derek S. Arndt, Mark A. Shafer and Kenneth C. Crawford Oklahoma Climatological Survey • Some prominent users of OCS’s drought package: • U.S. Drought Monitor Authors • Oklahoma Water Resources Board • (lead agency in OK state drought task force) • Oklahoma Fire Marshall and Governor’s Office • (“red flag” alerts, burn bans, etc.) Oklahoma Mesonet Oklahoma Climatological Survey OCS Drought Monitoring Philosophy: Six Guiding Principles For nearly ten years, OCS has monitored drought conditions with an expanding suite of real-time observations and products. Self-assessment using feedback from clients helped forge a drought monitoring philosophy. The following six tenets guide the ongoing development of OCS drought monitoring efforts: 1. Drought is a social phenomenon A widely accepted definition of drought is deceptively simple: It occurs when there is not enough water available to meet needs (Redmond 2002). This innocent definition dictates that responsible decision-makers, and those who provide their information, approach an understanding of drought through the lens of these needs. 2. Drought is relative in time, space and application Drought assessment must consider an ongoing interplay between scales. In Oklahoma, three intensifications of drought conditions occurred in the last five years: summer 1998 (~6 months with statewide impacts), late summer 2000 (~2 months with statewide impacts), and 2001-02 (12-14 months, greatest impact in state’s western half). Were these three separate events? Yes and no. To the state Fire Marshall, they were three separate and severe events that exacerbated wildfire conditions. To winter wheat farmers, they were three separate events whose impacts varied due to the time of year. To reservoir operators in southwestern Oklahoma, the period was essentially a single multi-year episode of varying intensity. Reservoir levels dropped and failed to recover throughout the period. 3. Because drought is intimately tied to society, a long-term reference is vital Society adjusts to nature over generations, and drought represents a departure of varying significance from nature’s long-term signal. Long-term averages are a major component of virtually all drought assessment indices, whether in the form of 30-year normals (e.g., for the Palmer Index) or the entire long-term record (e.g., for the Standardized Precipitation Index). Because people adjust, an objective measure of drought may have different impacts over time. For example, lessons learned during the great droughts of the 1930s radically changed farming practices in the Plains. As a result, the impacts of the multi-year 1950s drought in Oklahoma were less severe, even though objective measures indicate a severity on par with the 1930s. 4. New and emerging observational datasets should be explored Soil moisture observations from the Oklahoma Mesonet show a promising contribution to drought monitoring in the state. The ability to see both topsoil and subsoil moisture conditions provides a valuable verification tool that is measured independently of other drought-related variables. The observations are particularly effective during drought recovery, when they yield guidance on which precipitation events provide deep relief and which infiltrate just a few inches below the surface. The soil moisture dataset also offers opportunities for drought-related research. Decomposing long-term events into individual episodes of precipitation and drying will isolate the building blocks of drought and recovery. 5. Drought is a multi-faceted issue and requires a multi-faceted assessment Assessing drought is much like assessing illness: more than one type of assessment is often necessary. A doctor does not make a diagnosis based on one temperature measurement. Instead, the doctor may use that observation along with the results of other patient-appropriate and symptom-appropriate tests. That is, the doctor uses a well-chosen indicator in concert with other well-chosen indicators. A responsible drought decision-maker (and those who supply his data) should take the same approach. 6. Deliver drought information, not just drought data An independent survey of about 100 Oklahoma drought decision-makers indicated that real-time information significantly improves their drought decision process. However, many respondents believed that large doses of data become cumbersome if provided without any context of experience or history. Simply put, as the technology associated with delivering high-quality drought data improved, the ability to overwhelm clients with volumes of numbers became a real problem. Finding the best balance between data volume and usability is an ongoing effort at the Climate Survey. Because many drought managers are from non-meteorological or even non-scientific fields, OCS conveys information with sensitivity to the varying ways that adults process it. From an information perspective, several components of OCS’s drought information suite overlap, with the anticipation that at least one will resonate with the particular learning style and experience base of a client. Ten seasons are updated daily to provide the most appropriate time-scale for the client. Rankings and comparisons provide valuable historical perspective Basic statistics give a “traditional” view of the season’s precipitation Because many drought decision makers come from outside the geosciences, online help is available for each OCS drought product. Historical extremes provide “context of possibility” for the client Analog seasons appeal to personal and institutional memory. Drought indices provide “trigger” information for topsoil and subsoil interests “Finding the best balance between data volume and usability is an ongoing effort at the Oklahoma Climatological Survey.” Modeled fire danger and smoke management tools for fire personnel Summary maps provide at-a-glance assessment of statewide conditions Detecting a False Recovery September 2003 brought rain to drought-stricken parts of north central Oklahoma, ending extreme wildfire conditions and offering promise to the wheat farmers that comprise a large component of the region’s economy. Short term rainfall (30 days, upper left) and near-surface soil moisture (5 cm, lower left) suggested wet conditions across the region in mid-October. However, longer-term rainfall (120 days, upper right) and deeper soil moisture (75 cm, lower right) revealed that deep replenishment had not occurred in many areas. The scenario suggested a vulnerability to drought relapse if rains ceased, which was indeed the case. Seed that germinated rapidly in the shallow moisture was unable to access deeper soil water. This stunted early root and plant growth, which are very important to yield. Basic statistics can be misleading! In the above case, similar percent-of-normal values mask vastly different departures from historical norms. OCS drought products supply historical perspective alongside basic statistics. http://climate.ocs.ou.edu/rainfall_update.html