V8 Flashcards
Radiation balance – diurnal course:
Effects of longwave radiation – “beer garden”-microclimate:
- reduction of outgoing longwave radiation by absorption in the canopy
- back radiation from canopy and stems ⇒ less evening cooling, more comfortable microclimate
Strahlungsbilanz - verschiedene Landnutzungsarten:
Energy balance:
Energy balance:
Energy balance:
Energy balance:
Albedo:
- Rückstrahlungsvermögen von nicht selbstleuchtenden, diffus reflektierenden Oberflächen (z. B. Schnee, Eis)
Spatial approaches:
- remote sensing
Climate-vegetation interactions:
Carbon flux
Climate-vegetation interactions:
Air temperature
Climate-vegetation interactions:
Air temperature profiles in plant stands
Climate-vegetation interactions:
Air temperature profiles in plant stands
Climate-vegetation interactions:
Air temperature
- annual T-amplitude
Climate-vegetation interactions:
Air temperature profiles in plant stands
Climate-vegetation interactions:
Air temperature profiles in plant stands
Climate-vegetation interactions:
Air temperature in plant stands
Climate-vegetation interactions:
High-frequence variability
Climate-vegetation interactions:
Small-scale variability of temperature
- On what factors does horizontal T variability depend (e.g., in a field)?
- exposition
- radiation balance
- plant cover
- water ⇒ evapotranspiration
variability of ET can reach 20% in a field
Climate-vegetation interactions:
Temperature extremes: frost
- Frost: T2m <= 0°C
- late frost (in spring: damages e.g. in fruit / wine / horticulture)
- early frost (in autumn: threat to crops, e.g. potatoes, sugar beets)
- night frost (night radiation, cloudless, wind protected)
- snow cover often can be good frost protection
Climate-vegetation interactions:
Counter measures
- Frost irrigation for crops (especially fruit blossoming) in spring
- from +0.5°C continuous irrigation ⇒ thin layer of ice (solidification heat): T not significantly below freezing point over a longer period of time.
- only at rH > 80% and vwind < 2 m/s, otherwise evaporative cooling!
- no interruption of irrigation until T > 0°C
- high water input (up to 40000 L h-1 ha-1 water), soaking, leaching
Vorhersage von Frost:
- Indikatoren für Frost in den nächsten paar Tagen in den kritischen Phasen:
- wolkenlos
- Temperaturinversionslagen
- geringe Windgeschwindigkeiten (< 2 m/s)
- stabile Hochdrucklage
- Indikator für Spätfrost in der anstehenden Saison: SOI im Herbst immer negativ oder stark fallend
Other protective measures:
Other protective measures:
KaltlufteinbrĂĽche
(katabatische Fallwinde: zB Mistral, Bora):
Damage to plants due to temperature variations:
- Frost: volume expansion within the plant cells, rather: desiccation of the cells.
- Physiological drought and desiccation: in spring still frozen soil, conifers already have strong transpiration
- Heat: increased water demand due to increased assimilation, thickening of cell sap, desiccation (despite sufficient water supply in soil and air)
- damage by scorching (especially cereals in the ripening phase): if the T is too high ⇒ sugars are immediately converted into starch ⇒ grains stop growing ⇒ e.g. 3 subsequent days with T > 30°C • average cell death at 50 - 60°C
Relative humidity:
Relative humidity:
Humidity and CO 2:
Wind:
Vertical wind profile:
Excursus: Nature-based solutions against wind extremes
Windschutz:
Wind protection:
Combined effects of a wind protection by vegetation:
Nature-based solutions against wind extremes:
- often multiple rows of trees or shrubs perpendicular to the main wind direction
- range proportional to height
- dense shelters (walls, rows of houses, forests): strong reduction of wind speed, relatively short range, gustiness
- mainly coastal areas, lowlands, moors, high plateaus of low mountain ranges (e.g. sensitive vegetable crops in the Rhone Valley / Mistral)
