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Mikdat Kadioglu
and
Zekai Şen

Abstract

Degree-days are fundamental design parameters in many application fields such as power generation and consumption, agriculture, architecture, snow melt estimation, environmental energy planning, population siting, and military domains. Depending on temperature fluctuations, the degree-day statistics at any location show local and seasonal variations. Among these parameters the average degree-day durations for cooling and heating periods, degree-day sums, and their maximums play a significant role in practical applications. In the body of literature to date the average degree-day durations have been analytically studied most often for independent processes. In this paper, however, degree-day sums in addition to durations are considered as important design variables with analytical formulation for dependent processes on the basis of the first-order Markov process. The application of the methodologies developed are presented for five temperature measurement stations scattered throughout Turkey within different climate regions.

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Abdullah Kahraman
,
Mikdat Kadioglu
, and
Paul M. Markowski

Abstract

Severe convective storms occasionally result in loss of life and property in Turkey, a country not known for its severe convective weather. However, relatively little is known about the characteristics of Turkish severe weather environments. This paper documents these characteristics using European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis data on tornado and severe hail days in Turkey from 1979 to 2013. Severe storm environments are characterized by larger convective available potential energy (CAPE) in Turkey compared to the rest of Europe, but the CAPE values are less than those in typical U.S. severe storm environments. Severe hail is associated with large CAPE and vertical wind shear. Nonmesocyclonic tornadoes are associated with less CAPE compared with the other forms of severe weather. Deep-layer vertical wind shear is slightly weaker in Turkish supercell environments than in U.S. supercell environments, and Turkish tornadic supercell environments are characterized by much weaker low-level shear than in the United States and Europe, at least in the ECMWF reanalysis data. Composite parameters such as the supercell composite parameter (SCP) and energy–helicity index (EHI) can discriminate between very large hail and large hail environments.

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Abdullah Kahraman
,
Şeyda Tilev-Tanriover
,
Mikdat Kadioglu
,
David M. Schultz
, and
Paul M. Markowski

Abstract

A climatology of severe hail (diameter equal to or exceeding approximately 1.5 cm) for Turkey is constructed from official severe weather reports from meteorological stations, newspaper archives, and Internet sources. The dataset consists of 1489 severe hail cases on 1107 severe hail days (days with at least one severe hail case) during 1925–2014. Severe hail was reported most often in the 1960s, followed by a decrease until the 2000s, and an ensuing increase in the past decade. Severe hail is most likely to occur in the afternoon and evening, and in spring and summer, particularly May and June. The geographical distribution implies that almost all of Turkey is prone to severe hailstorms. In 8.3% of the severe hail cases, very large hailstones (diameter equal to or exceeding approximately 4.5 cm) were observed.

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