Hydrometeorology

Weather phenomena refer to short-term physical conditions observed in the atmosphere at a specific time and location. These phenomena are typically defined by the observation of meteorological variables such as temperature, wind, humidity, pressure, cloud cover, and types of precipitation. Phenomena such as rain, snow, hail, fog, lightning, and storms are among the most commonly encountered weather events. These events not only reflect the state of the atmosphere but also directly impact land, sea, and human activities.

Meteorology is the scientific discipline that studies physical and chemical processes in the atmosphere, focusing on the observation, analysis, and prediction of weather phenomena. This field is divided into sub-disciplines such as synoptic meteorology, dynamic meteorology, and applied meteorology, each examining atmospheric events at different scales. In this context, hydrometeorology emerges as an interdisciplinary research area at the intersection of meteorology and hydrology.

Hydrometeorology focuses on the movement of atmospheric water over land, particularly examining processes such as precipitation, evaporation, soil moisture, runoff, and snowmelt. In other words, this field evaluates all interactions from the moment precipitation falls on the land surface until it becomes part of groundwater and surface water systems, within the context of atmospheric conditions. Therefore, hydrometeorology plays a fundamental role not only in weather monitoring but also in applications such as flood forecasting, drought monitoring, water resource planning, and disaster risk management.

Data used in hydrometeorological analyses typically include measurements of precipitation amount, temperature, wind direction and speed, relative humidity, groundwater level, and river discharge. When combined with long-term observational series, these data enable both short-term forecasting and the analysis of climatic trends.

Furthermore, hydrometeorological events are inherently influenced by both natural and anthropogenic processes. For example, urbanization and changes in land use can disrupt the precipitation-runoff balance, increasing flood risk, while climate change can alter the frequency and intensity of extreme weather events. This situation underscores the necessity of jointly analyzing weather phenomena and the water cycle.

In conclusion, hydrometeorology is a field that requires a holistic analysis of both atmospheric and hydrospheric processes. Therefore, an interdisciplinary approach, observational accuracy, and modeling capability are among its foundational pillars.

Interaction Between Atmospheric and Hydrological Processes

Atmospheric and hydrological processes are inseparable components of the natural water cycle. The interaction between these processes is critically important for understanding both daily weather events and long-term climatic changes. The discipline of hydrometeorology examines energy and mass transfers within the land-atmosphere system by evaluating these two processes within a common framework.

Atmospheric processes include phenomena such as evaporation, cloud formation, precipitation, and wind motion, which are driven by external energy sources, primarily solar radiation. A significant portion of these processes begins with the entry of water vapor into the atmosphere. Water evaporated from lakes, rivers, seas, and soil surfaces condenses in the atmosphere to form clouds and returns to the Earth’s surface as precipitation under suitable conditions. This cycle affects not only the amount of water in the atmosphere but also atmospheric pressure, temperature, and wind patterns.

Hydrological processes encompass the movement of precipitation on the Earth’s surface through groundwater and surface water systems. This includes infiltration of precipitation into the soil, conversion to surface runoff, infiltration into groundwater, and transport via rivers. The intensity, duration, and type of precipitation directly determine how these processes operate. For instance, a heavy and short-duration downpour can trigger surface runoff before the soil can absorb sufficient water, thereby increasing flood risk.

The interaction between these two processes is particularly significant in the following areas:

• Flood formation: Sudden and intense precipitation from the atmospheric system can exceed the capacity of the hydrological system, resulting in flooding. This effect is especially pronounced in urban areas due to increased surface impermeability.
• Drought: Prolonged reductions in precipitation lead to declines in hydrological indicators such as soil moisture, groundwater levels, and river discharge. This process threatens both agricultural production and drinking and irrigation water supplies.
• Snowmelt processes: Sudden increases in atmospheric temperature, particularly during spring months, can cause rapid melting of snow cover. This can lead to flooding as the meltwater contributes to river flow.
• Soil moisture and evaporation relationship: High soil moisture supports surface evaporation, while prolonged drought periods restrict evaporation and thereby affect the atmospheric water cycle.

Modeling these interactions is of great importance for predicting hydrometeorological events. Integrated models that consider both atmospheric and hydrological processes are widely used across a broad range of applications, from flood early warning systems to drought analysis.

In conclusion, the mutual interaction between atmospheric and hydrological processes provides a fundamental analytical framework for water resource management, disaster prediction, and the development of climate change adaptation strategies. A correct understanding of this framework directly influences the success of both scientific and applied studies.

Main Weather Phenomena and Classifications

Weather phenomena can be defined as the surface manifestations of physical processes occurring in different layers of the atmosphere. These phenomena are classified in various ways based on their observable characteristics, formation mechanisms, and impacts. Within the discipline of hydrometeorology, these phenomena are particularly evaluated in the context of water vapor transformation processes such as condensation, sublimation, and freezing.

Precipitation Events

Precipitation is the descent of condensed water vapor from the atmosphere to the Earth’s surface in liquid or solid form. Precipitation types are classified as follows based on temperature conditions and physical transformations in the atmosphere:

• Rain: The most common type of liquid precipitation.
• Snow: Formed by the aggregation of ice crystals under atmospheric conditions below freezing point.
• Hail: Ice particles that grow within strong convective clouds (cumulonimbus) due to upward and downward air movements.
• Drizzle: Defined as very small and slowly falling liquid droplets.
• Sleet: Snowflakes that have partially melted during their descent.

Visibility-Reducing Events

Weather events that reduce visibility are generally caused by microscopic water droplets or ice crystals suspended in the atmosphere:

• Fog: Forms due to condensation of water vapor in the atmospheric layer near the surface.
• Haze: A semi-transparent atmospheric pollution caused by dust, smoke, or salt particles.
• Smoke: Particles resulting from combustion can accumulate in the atmosphere and reduce visibility.

Convective and Dynamic Events

These types of events occur when atmospheric equilibrium is disrupted:

• Storm: A weather system characterized by strong winds, heavy precipitation, and lightning.
• Lightning and Thunder: Electrical discharges occur between clouds or between clouds and the Earth’s surface due to charge differences.
• Tornado and Waterspout: Rotating wind systems with extremely low-pressure centers. They commonly form where moist and warm air masses collide with cold air.

Wind Events

Wind is the horizontal movement of air resulting from pressure differences in the atmosphere. It is classified according to its speed and direction:

• Local winds such as meltem, lodos, and poyraz exhibit regional effects;
• Systems such as hurricanes and typhoons are tropospheric structures affecting large areas.

Extreme Weather Events

Events that have increased in frequency and impact in recent years are evaluated as a distinct category:

• Events such as heatwaves, sudden floods, droughts, and heavy snowfall develop beyond the normal limits of atmospheric systems.
• These events are important subjects of study due to both their short-term impacts (e.g., loss of life, infrastructure damage) and long-term consequences (e.g., agricultural production loss, water scarcity).

This classification of weather phenomena greatly facilitates the analysis of observational data and modeling and forecasting studies. Moreover, since each type of event requires specific monitoring techniques and intervention strategies, this classification provides a critical framework for disaster management.

Hydrometeorological Observation and Data Collection Methods

Accurate monitoring and prediction of hydrometeorological events depend on reliable observation systems and comprehensive data collection methods. These observation systems are designed to monitor atmospheric variables and surface water processes. Observation data enable real-time decision support systems and facilitate the identification of long-term climatic trends.

Surface Observation Stations

Meteorological stations measure fundamental meteorological parameters such as air temperature, wind speed and direction, humidity, precipitation amount, and atmospheric pressure. These stations are distributed across terrestrial areas and transmit data at regular intervals. In Türkiye, this responsibility is primarily carried out by the General Directorate of Meteorology (MGM) and related institutional structures.

Hydrological observation stations measure variables such as river discharge, water level, and temperature. These stations play a fundamental role in flood monitoring and water resource management.

Automatic Meteorological Measurement Systems (AMMS)

Automatic sensors are increasingly replacing traditional observation systems, providing continuous and high-frequency data. These systems operate without human intervention and can be installed at various altitudes. Multiple variables such as temperature, wind, radiation, soil moisture, and precipitation can be monitored simultaneously.

Radar Systems

Meteorological radars are primarily used to observe convective systems such as sudden downpours or hailstorms. These radars analyze electromagnetic waves reflected by water droplets within clouds to determine the intensity, type, and movement direction of precipitation. Radar data are among the most important inputs for short-term forecasting (nowcasting).

Satellite Systems

Meteorological satellites observe parameters such as cloud cover, surface temperature, sea surface height, ice cover, and humidity profiles over large geographic areas. Geostationary and polar-orbiting satellites provide atmospheric monitoring at different resolutions. These data are critical for applications such as tropical storm monitoring and climate model initialization.

Remote Sensing Technologies

Lidar (Light Detection and Ranging) and Radar altimeters enable high-resolution analysis of detailed water movements in the atmosphere and at the surface. These technologies allow the determination of parameters such as cloud height, vertical precipitation profiles, snowpack thickness, and soil moisture.

Ground-Based Observations and Hydrographic Measurements

Manual or semi-automatic measurement systems for dams, rivers, lakes, and groundwater systems are still used, particularly for water level and water temperature monitoring. Additionally, field surveys and post-flood site investigations provide validating data for modeling.

Data Collection and Distribution Infrastructure

The integration, modeling, and analysis of collected data are carried out through national data networks and international systems. In Türkiye, institutions such as MGM, DSİ, and AFAD manage this infrastructure, while globally, organizations such as WMO (World Meteorological Organization) and EUMETSAT oversee it.

Thanks to these measurement systems, weather events and water cycle processes can be analyzed quantitatively. The obtained data serve both as inputs for early warning systems and as scientific inputs forming the basis of climate policies.

Hydrometeorological Models and Forecasting Systems

Hydrometeorological forecasts are based on mathematical representations of atmospheric and hydrological systems. These forecasts are essential tools for anticipating and mitigating the impacts of events such as flash floods, heavy rainfall, droughts, and snowmelt. Developed models analyze atmospheric-water-related processes in space and time using processed observational data.

Numerical Weather Prediction Models (NWP)

Numerical weather prediction models are computational systems that represent physical processes in the atmosphere using differential equations. These models use real-time observational data as initial conditions and are run on high-performance computers.

Main models include:

• ECMWF (European Centre for Medium-Range Weather Forecasts)
• GFS (Global Forecast System – USA)
• WRF (Weather Research and Forecasting Model) – commonly used for local weather forecasting.
• These models can forecast numerous meteorological parameters such as temperature, wind, humidity, precipitation, and cloud cover from 1 hour to 15 days ahead.

Hydrological Forecasting Models

Hydrological models simulate the transformation of precipitation falling on the land surface into runoff, evaporation, or groundwater. These models are critically important for flood forecasting and water resource management studies.

Commonly used hydrological models:

• HEC-HMS (Hydrologic Modeling System): Developed by the U.S. Army Corps of Engineers; widely used for modeling precipitation-runoff processes.
• MIKE SHE: A system capable of modeling the entire hydrological cycle on a physical basis.
• SWAT (Soil and Water Assessment Tool): Focuses on long-term simulation of water quality and quantity in agricultural areas.

Integrated Hydrometeorological Models

Integrated models that simulate both atmospheric and hydrological systems form the basis of flood forecasting and early warning systems. These systems use weather forecast data as inputs to hydrological models. Thus, for example, the amount of predicted precipitation in a specific region that will contribute to flooding can be calculated.

Data Assimilation Techniques

To improve model accuracy, real-time observational data must be continuously updated into model inputs. This process is called data assimilation. Particularly radar, satellite, and ground measurement data enable continuous revision of model outputs. This technique significantly reduces forecast errors, especially in short-term predictions.

Long-Term Forecasting and Climate Projections

Unlike daily weather forecasts, seasonal forecasts and climate scenarios aim to determine average temperature and precipitation trends. These projections are used to predict hydrological impacts of climate change. Models such as GCM (Global Circulation Model) and RCM (Regional Climate Model) have been developed for this purpose.

Early Warning and Decision Support Systems

The outputs of hydrometeorological models are integrated into early warning systems that guide decision-makers in disaster management and water resource planning. These systems establish automatic alarm mechanisms when specific threshold values are exceeded, contributing to strategic planning aimed at preventing potential damage.

In conclusion, modeling and forecasting systems not only predict weather and water events in advance but can also be applied across diverse fields such as infrastructure design, agricultural production planning, and disaster preparedness. These systems, which are continuously improved based on factors such as model reliability, observation quality, spatial resolution, and update frequency, constitute the cornerstone of modern hydrometeorology.

Hydrometeorological Disasters and Risk Management

Hydrometeorological disasters are events in which atmospheric and hydrological processes exceed their normal limits, causing destructive impacts on human life, the environment, and economic systems. These disasters typically arise from short-term and intense weather events or long-term climatic anomalies. Risk management is an integrated process aimed at reducing the probability, intensity, and impacts of such events.

Main Types of Hydrometeorological Disasters

Flash Floods

Formed when excessive precipitation over a short period rapidly converts to surface runoff in narrow watersheds. Often causes severe loss of life and property, especially in urbanized areas due to infrastructure impermeability.

River Floods

Occur when river discharge rises due to prolonged rainfall or snowmelt, causing water to overflow its channel. Affects large areas and impacts agriculture, settlements, and transportation infrastructure.

Drought

Has subtypes such as meteorological drought (precipitation deficit), hydrological drought (decline in river and groundwater levels), and agricultural drought (reduction in soil moisture). Due to its persistence, its economic impact is broader and deeper than that of floods.

Snowmelt Floods

Triggered by sudden temperature increases or rainfall during spring, leading to snowmelt. Particularly impactful in high-altitude regions.

Storms, Hail, and Extreme Temperatures

Strong winds, sudden hailstorms, and heatwaves also fall under the category of hydrometeorological disasters. They can directly affect agriculture, energy, health, and transportation systems.

Components of Disaster Risk Management

Risk Assessment and Mapping

Risk maps for floods, drought indices, and disaster scenarios are developed to determine where, when, and to what extent risks may occur.

Early Warning Systems

Forecasting systems based on observational data provide warnings hours or even days before an event occurs. Automatic alarm systems, sirens, SMS alerts, and mobile applications inform the public.

Structural Measures

Dams, levees, floodplain management, and urban infrastructure provide physical solutions to reduce flood risk. However, they are insufficient on their own.

Non-Structural Measures

Include social and institutional tools such as early warning education, risk awareness campaigns, land-use planning, and insurance systems. These measures play a critical role in building community resilience to disasters.

Post-Disaster Response and Recovery

Effective disaster management includes not only pre-event preparedness but also post-event recovery processes. Evacuation plans, temporary shelter solutions, healthcare services, and infrastructure repair are components of this process.

Institutional and Legal Frameworks

In Türkiye, hydrometeorological disaster management is carried out through shared responsibilities among various public institutions, primarily AFAD, MGM, DSİ, and the Ministry of Environment, Urbanization and Climate Change. National disaster risk reduction plans such as TARAP ensure coordination among these institutions. Internationally, the Sendai Framework for Disaster Risk Reduction (2015–2030) encourages countries to adopt risk-based approaches.

In conclusion, preventing hydrometeorological disasters and reducing their impacts requires not only technical solutions but also a holistic risk management approach encompassing social, institutional, and ecological dimensions. This approach has become even more vital in today’s world, where the impacts of climate change are intensifying.

Climate Change and Its Impacts on Hydrometeorology

Climate change is fundamentally reshaping the relationship between the atmosphere and the water cycle, affecting both the characteristics of short-term weather events and long-term hydrological balance. From the perspective of hydrometeorology, climate change means not only rising temperatures but also structural transformations in precipitation regimes, evaporation rates, drought frequencies, and extreme event patterns.

Changes in Precipitation Regimes

Climate change alters the spatial and temporal distribution of precipitation globally. While some regions experience increased total precipitation, others face significant declines. Simultaneously, higher atmospheric temperatures have increased the atmosphere’s capacity to hold water vapor, leading to more intense precipitation over shorter durations. The increased frequency and intensity of convective storms are elevating flood risk.

Drought Probability and Duration

Increased evaporation reduces soil moisture, raising the risk of agricultural drought. At the same time, hydrological drought (declines in river discharge and groundwater levels) is becoming more prolonged. This situation threatens the sustainability of water resources, particularly in semi-arid and arid regions.

Snow Cover and Melt Dynamics

Rising temperatures are reducing snowfall amounts and causing existing snowpacks to melt earlier. This alters the timing of snowmelt-induced floods, creating uncertainty in flood forecasting models. It may also shift the timing of reservoir filling.

Frequency and Intensity of Extreme Weather Events

Increased energy in the climate system enhances atmospheric instability, increasing both the number and impact of extreme weather events such as hail, storms, heatwaves, and sudden rainfall. These events are now observed not only in extreme climate zones but also in temperate regions. This shift may render existing hydrometeorological infrastructure inadequate.

Soil Moisture Dynamics and Evaporation

Soil moisture is a critical parameter for both agricultural production and groundwater recharge. Rising temperatures accelerate surface evaporation, leading to faster loss of soil moisture. This process increases the risk of water stress, particularly during plant growth periods.

Implications for Hydrometeorological Modeling

Climate change necessitates the reconfiguration of traditional hydrological and meteorological modeling methods. Since past-based forecasts are no longer sufficient, climate scenario-based projection models (e.g., RCP scenarios) are now being employed. These models enable predictions of potential hydrological and meteorological changes over the next 10 to 100 years.

In conclusion, climate change directly affects the scope and application tools of hydrometeorology. To adapt to these impacts, not only technical approaches but also legal, institutional, and social strategies must be developed. Risk-based, climate-resilient, and integrated approaches will be among the most critical priorities for the coming era.

Hydrometeorology Applications and Institutional Structure in Türkiye

Türkiye, due to its complex topography, being surrounded by seas on three sides, and its position under the influence of different climate zones, experiences a wide variety of hydrometeorological events. Consequently, hydrometeorological applications in Türkiye have a broad structure at both research and public service levels. Various institutional structures operate in areas such as weather monitoring, water resource assessment, and flood and drought forecasting.

General Directorate of Meteorology (MGM)

The General Directorate of Meteorology is the primary institution in Türkiye responsible for meteorological observation, analysis, and forecasting. Hundreds of observation stations, radar systems, and automatic meteorological measurement systems located across all 81 provinces and rural areas continuously monitor parameters such as temperature, pressure, wind, humidity, and precipitation. MGM also provides services such as flood early warning, weather forecasting, climate assessment reports, and agricultural meteorology.

General Directorate of State Hydraulic Works (DSİ)

DSİ is the institution responsible for observing, developing, and managing Türkiye’s surface and groundwater resources. Hydrological data such as river discharge, water levels, and reservoir fill rates are collected by DSİ. DSİ also plays an active role in flood control projects, irrigation infrastructure, and drought mitigation strategies.

Disaster and Emergency Management Presidency (AFAD)

AFAD is responsible for reducing and managing the impacts of hydrometeorological disasters such as floods, droughts, and storms. Based on data received from MGM and DSİ, it develops scenario-based risk analyses, manages early warning systems, and coordinates emergency response plans. Local disaster risk reduction plans are also implemented under this framework.

Universities and Research Institutions

Universities in Türkiye with departments in meteorological engineering, hydrology, environmental engineering, and geology conduct both academic research and applied modeling studies. Particularly Istanbul Technical University, Middle East Technical University, Ege University, Çukurova University, and Ankara University are specialized centers in this field. Universities collaborate with DSİ and MGM to develop flood, drought, and water resource modeling based on climate scenarios.

National and International Projects

In Türkiye, hydrometeorological data infrastructure is being strengthened within frameworks such as EU-supported climate adaptation projects, national climate strategy documents, and Green Accord Compliance Plans. The “National Drought Management Strategy” and “Flood Management Plans” emphasize data-driven and locally focused risk-based planning. Türkiye also engages in information sharing with the World Meteorological Organization (WMO) and the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT).

Legislation and Policy Documents

Main legal documents guiding hydrometeorological applications include the Meteorological Services Law, the Draft Water Law, the National Climate Change Action Plan, and the Türkiye Disaster Risk Reduction Plan 2023–2030 (TARAP). These documents contain fundamental provisions on data sharing, inter-institutional coordination, establishment of early warning systems, and development of publicly accessible risk maps.

In conclusion, the hydrometeorological structure in Türkiye is managed through a multi-actor and multi-level system. However, enhancing institutional coordination, expanding early warning systems, and strengthening planning based on climate change scenarios remain priority areas. Developing interdisciplinary knowledge production and data sharing mechanisms offers a critical strategic direction for reducing future hydrometeorological risks.