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2. Modelovanie vodnej hodnoty snehu v horskom povodí distribuovaným modelom akumulácie a topenia snehu
- Creator:
- Holko, Ladislav, Parajka, Juraj, and Kostka, Zdeno
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- distributed snow accumulation and melt model, energy balance, degree-day, mountain catchment, atmospheric precipitation, distribuovaný snehový model, metóda energetickej bilancie, metóda teplotného faktora, horské povodie, and atmosférické zrážky
- Language:
- Slovak
- Description:
- The objective of this paper is to compare the results of two distributed snow models based on different approach to snow accumulation and melt. Model WaSiM is based on the degree-day approach, while model UEB-EHZ is an energy-based model. Simulations in the mountain catchment of Jalovecký creek in winters 1989-2001 showed that both approaches can produce similar results. Model parametrization is more important than basic approach to snow accumulation and melt. Therefore, model UEB-EHZ which took into acccount influence of forest on radiation reduction and snow drift, performed better for the forest sites. The paper presents also brief overview of snow accumulation and melt modelling including calibration and verification of distributed models. Finally, it shows some outupts which can be provided by distributed snow models. and Príspevok je venovaný porovnaniu dvoch distribuovaných matematických modelov akumulácie a topenia snehu s rôznym prístupom k modelovaniu snehu. V horskom povodí Jaloveckého potoka boli hodnotené výsledky energeticky založeného modelu UEB-EHZ a modelu WaSiM, vychádzajúceho z metódy teplotného indexu pre zimy 1988/89 - 2000/2001. Porovnanie výsledkov oboch modelov ukázalo, že pokiaľ ide o základný prístup k modelovaniu topenia snehu (energetická bilancia alebo teplotný index), nemohli sme v danom povodí určiť, ktorý z nich viedol k lepším výsledkom. Väčší vplyv na simuláciu vodnej hodnoty snehu ako výber základného prístupu k modelovaniu akumulácie a topenia snehu, má parametrizácia konkrétneho modelu. V modeli UEB-EHZ bol napríklad čiastočne zahrnutý vplyv lesa na globálne žiarenie a podmienky ukladania snehu (drift). Preto bolo topenie snehovej pokrývky v lese týmto modelom simulované reálnejšie ako modelom WaSiM. Okrem porovnania výsledkov dvoch základných prístupov k modelovaniu akumulácie a topenia snehu v horskom povodí príspevok ukazuje aj niektoré výstupy, ktoré možno získať pomocou distribuovaného snehového modelu a stručne sa zaoberá diskusiou o kalibrácii a validácii takéhoto modelu.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
3. The Lyman α line in the solar chromosphere: penetrative model and approximations
- Creator:
- Faurobert, M., Frisch, H., and Skumanich, A.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- solar chromosphere, Lyman α line, and energy balance
- Language:
- Czech
- Description:
- A multi-level calculation of the hydrogen spcctrum by Skumanich and Lites, followed by a two-level rcpresentation of each transition, shows that all the solar Lyman α photons are created in the high chromosphere, above ro^ ≃ 10^2 (ro denote the optical depth at the center of the line). Below this depth the Lyman α line is only fed by multiple scatterings. The source function decreases, first very slowly and then as ro^ ≃ 10^7. The change in slope occurs at ro^ ≃ 10^5. We shall present a model for the formation of Lyman α in the chromosphere below the creation region. The hydrogen atom is treated as a two-level atom and the chromosphere as a semi-infinite medium free of primary sources and illuminated by an isotropic and frequency independent radiation field at ro^ ≃ 10^2. A second order escape probability approximation fields a simple analytical expression which accurately reproduces the behaviour of the Lyman α source function between ro ≃ 10^2 and 5 10^6 provided the destruction probability is set close to 10“-6. This value agrees very well with that obtained by Skumanich and Lites for the generalized Lyman α destruction probability in the low chromosphere.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
4. Thermal dissipation during photosynthetic induction and subsequent dark recovery as measured by photoacoustic signals
- Creator:
- Buschmann, C.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- chlorophyll fluorescence, energy balance, heat production, induction kinetics, and photoacoustic spectroscopy
- Language:
- Multiple languages
- Description:
- The thermal photoacoustic signal (279 Hz) and the chlorophyll (Chl) fluorescence of radish cotyledons (Raphanus sativus L.) were measured simultaneously. The signals were recorded during a photosynthetic induction with actinic radiation of different quantum fluence rates [20, 200, and 1200 µmol(PAR-quantum) m-2 s-1]. The rise of these signals upon irradiation saturating photosynthesis was followed in the steady state of the induction and during the subsequent dark-recovery (i.e., in dark periods of 1, 5, 15, and 45 min after the induction). From these values various parameters (e.g., quantum yield, photochemical loss, different types of quenching coefficients) were calculated. The results show that heat dissipation detected by photoacoustic measurements is neither low, constant, nor always parallel to Chl fluorescence. Therefore, the thermal signal should always be measured in order to fully understand the way leaves convert energy taken up by PAR absorption. This helps in the interpretation of photosynthesis under different natural and anthropogenic conditions (stress and damage effects).
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public