Agricultural Meteorology

Agricultural Meteorology is a scientific discipline that studies the effects of physical phenomena in the atmosphere on agricultural production and the behavioral responses and reactions of living organisms—including economically significant crop plants, livestock animals, insects, and pathogenic microorganisms—to their physical environment. Recognized as a subfield of meteorology, agricultural meteorology focuses on the use and interpretation of a large portion of meteorological data in agriculture.

The primary objective of this discipline is to provide producers and farmers with the necessary information and warnings regarding climate and weather conditions to enhance the yield and quality of agricultural production, minimize potential damages caused by adverse weather conditions, and ensure the economic use of agricultural inputs such as fertilizers, pesticides, and labor. According to an assessment by the World Meteorological Organization (WMO), the cost-benefit ratio of meteorological services in agriculture is 1:15, meaning that for every unit of cost spent on weather forecasting, 15 units of benefit are generated in agriculture.

Historical Development

The earliest records of the impact of weather and climate on agriculture date back to Roman and Chinese civilizations. The history of phenological calendars, which track developmental stages of living organisms, extends as far back as 500 BCE. The invention of instruments such as the hydrometer (1593) and the barometer (1643) during the Renaissance laid the groundwork for advancements in this field.

The institutionalization of the relationship between agriculture and meteorology at the international level began with the establishment of the "Commission on Agricultural Meteorology" within the International Meteorological Organization (IMO) in 1913. Work was interrupted due to World War I but resumed after the commission was re-established in 1919 and has continued since 1951 under the auspices of the World Meteorological Organization (WMO), a specialized agency of the United Nations.

In Türkiye, the origins of agricultural meteorology applications developed in parallel with the institutionalization of agricultural education. In 1891, an observatory section was established within the Halkalı Higher Agricultural School, where meteorological observations such as temperature, humidity, precipitation, wind direction, and wind speed were conducted. These observations were regularly published in the school’s publication, the Halkalı Higher Agricultural School Journal. Modern agricultural education continued with the establishment of the Higher Agricultural School in Ankara in 1930 and its successor, the Higher Institute of Agriculture. From 1955 onward, the opening of new agricultural faculties within Ankara University, Aegean University, Atatürk University, and Çukurova University expanded agricultural education and, consequently, research in agricultural meteorology.

Conceptual Framework and Relationship with Other Disciplines

Agricultural meteorology maintains close ties with meteorology and climatology but possesses its own distinct approach and area of study.

Meteorology and Agricultural Meteorology

Meteorology generally examines atmospheric phenomena and processes, presenting data in raw or generalized terms. For example, synoptic meteorology may report that the lowest temperature in a region was 3°C, while agricultural meteorology interprets this same value in terms of frost risk for local crop species or as accumulated heat units affecting plant development. Similarly, hydro-meteorology may report total monthly precipitation as 45 mm, whereas agricultural meteorology evaluates whether this amount meets the water needs of local plants and determines if and how much irrigation is required.

Climatology and Agricultural Meteorology

Climatology studies long-term averages, deviations, and climate types of atmospheric phenomena over many years. It essentially functions as a database and analytical framework for processed meteorological data. Agricultural meteorology takes these climatological data—such as frost calendars, prevailing wind directions, and long-term averages of precipitation and temperature—and develops specialized interpretations and plans for agricultural applications such as farm planning, crop pattern selection, and drought analysis.

Climate Conditions Monitored for Livestock Productivity (Generated by Artificial Intelligence)

Areas of Study and Applications

Agricultural meteorology transforms meteorological data into actionable information for every stage of agricultural production. Its main areas of study include:

Analysis of Meteorological Parameters and Their Agricultural Impacts

Temperature

The temperature range required for plants to sustain vital activities generally varies between 0–54°C. Agricultural meteorology examines the minimum, optimal, and maximum temperatures required by different crops for germination, growth, and development. It also investigates the following:

• Effective Temperature Summation (Degree-Days): Calculates the total heat accumulation required for crop maturity.

• Chilling Requirement (Vernalization): Determines the duration plants, particularly deciduous fruit trees, must be exposed to temperatures between 0–7°C to initiate budbreak and ensure productivity.

• Soil Temperature: Directly affects seed germination, root development, and microbial activity in soil (e.g., nitrification).

• Temperature Stress: Analyzes adverse effects of high temperatures on livestock, such as reduced milk and reproductive yields.

Wind

Wind plays a role in plant transpiration, soil evaporation, and the dispersal of seeds and disease spores. The optimal wind speed for plants is generally considered to be 3–5 m·s⁻¹; however, speeds exceeding 10 m·s⁻¹ can cause mechanical damage and wind erosion.

Humidity

Decreasing air humidity combined with rising temperatures increases evaporation, while humid conditions create favorable environments for the proliferation of plant diseases and fungi. Soil moisture is a critical factor for seed germination, root development, and nutrient uptake; deficiency leads to wilting, while excess causes root rot.

Precipitation

Light drizzle, rain, and snow are the most beneficial forms of precipitation for agriculture. Snow cover acts as an insulating layer that protects plants from freezing during winter months. Hail, however, is a destructive form of precipitation that causes significant damage, particularly during the growth phase of crops and in fruit orchards.

Sunlight and Radiation

Light directly influences physiological processes such as chlorophyll formation, photosynthesis, transpiration, and hormone production. Cloud cover reduces sunlight and temperature while increasing humidity and precipitation, potentially promoting certain fungal diseases.

Analysis and Forecasting of Agricultural Meteorological Events

Frost Events

One of the most damaging meteorological events in agriculture. Agricultural meteorology classifies frost events by their formation type (radiation frost and advection frost), timing (late spring frosts and early autumn frosts), and intensity. It develops both passive (site selection, crop selection, soil tillage methods) and active (heaters, wind machines, sprinkler irrigation) protective measures and operates early warning systems to mitigate frost risk.

Drought

Drought, generally defined as water deficiency, occurs when precipitation falls below normal levels. Agricultural drought is specifically defined as the point at which available soil moisture drops to the wilting point of plants. Drought analyses are typically conducted using methods such as the Standardized Precipitation Index (SPI), Percent of Normal Index (PNI), and Palmer Drought Severity Index (PDSI).

Forest Fires

Agricultural meteorology plays a key role in assessing the risk of forest fires. Parameters such as air temperature, relative humidity, wind speed, and the time elapsed since the last precipitation influence the moisture content of forest floor litter (fuel), thereby determining fire risk.

Phenological Observations

The monitoring and recording of key developmental stages in plants and animals, such as budburst, flowering, harvest, and migration. These observations enable the determination of optimal crop patterns and planting-harvesting schedules for a given region.

Erosion

Water and wind erosion are processes that remove the fertile topsoil layer. Agricultural meteorology analyzes factors such as rainfall intensity and wind speed to assess erosion risk and supports the planning of protective farming techniques such as windbreaks and strip cropping.

Institutional Products and Services

In Türkiye, the General Directorate of Meteorology (MGM) provides various products and services to the agricultural sector through its Agricultural Meteorology Sub-Directorate. These services include:

• Agricultural Weather Forecasts: Five-day weather forecasts are prepared daily for nine agricultural regions defined by the Ministry of Food, Agriculture and Livestock.

• Agricultural Frost Warning System (AFWS) and Frost Risk Maps: A web application that displays frost risk and expected minimum temperatures for the next four days based on the user’s selected province, district, crop, and phenological stage. Daily frost risk maps are also published.

• Türkiye Frost Calendar: A comprehensive study using long-term data (1971–2010) from 354 stations across Türkiye to determine and map the latest spring and earliest autumn frost dates for various temperature thresholds (−4, −3, −2, −1, and 0°C).

• Drought Analysis and Monitoring System (DAMS): Monthly drought maps and analyses are generated for 3, 6, 9, 12, and 24-month periods using the SPI method.

• Irrigation Planning System (SUPSİS): Uses reference crop evapotranspiration values calculated by the FAO Penman-Monteith method to show daily water deficits or surpluses and supports irrigation planning.

• Harvest Time Prediction Program: Estimates harvest dates based on the growth degree-day (effective temperature summation) method, using planting date and crop type.

• Temperature-Humidity Index (SİNEP) Program: Calculates the Temperature-Humidity Index using ambient temperature and relative humidity to assess heat stress in dairy cattle and provides a three-day forecast.

• Plant Chilling Requirement Program (BİSİP): Calculates whether the chilling requirement of fruit trees during winter is met, using hourly temperature data.