Testing the α and β methods of estimating evaporation from bare and vegetated surfaces in class
Notice bibliographique
Résumé
Abstract Surface soil wetness determines whether evaporation occurs at the potential rate or is limited by soil water supply. Many land surface models calculate evaporation by parametrizing the relative humidity at the soil surface (α method) or the soil water diffusion resistance (β method). The relationships of α and β to the average moisture content of soil surface layer thicknesses ranging from 0.5 to 10 cm were examined using Bowen ratio/energy balance measurements of evaporation from a bare loam/silt‐loam soil at two adjacent sites, one of which was culti‐packed while the other was disc‐harrowed. It was found that the relationships were sensitive to the surface layer thickness and tillage treatment and became better defined with larger thicknesses. Simulations of evaporation by CLASS (Canadian Land Surface Scheme) using Philip's relationship (currently used in CLASS to determine α with a 10‐cm thick surface soil layer) and our proposed relationships of α and β were compared with measurements made during a 7‐day drying period for the culti‐packed soil. Evaporation was significantly overestimated by Philip's relationship when the soil was dry. The α and β relationships gave much better estimates of evaporation than Philip's relationship; however, evaporation under conditions of high air humidity (e.g., night‐time) was significantly suppressed by the α relationship. In long‐term simulations, there were large differences between simulated and measured evaporation rates due to differences between actual and calculated soil moisture. When CLASS was forced to use measured soil moisture, evaporation rates calculated using the β relationship agreed remarkably well with the measured values, while those calculated using Philip's relationship were significantly overestimated. The effectiveness of the β relationship was also tested with a 2‐cm thick surface layer using data collected from another bare silt loam soil and for a 10‐cm thick surface layer using data from a crop and two forests with different soil types. It gave better estimates of evaporation from these surfaces than Philip's relationship. In the simulation with CLASS, the β relationship appeared less sensitive to possible errors in modelled drainage than Philip's relationship, and was recommended for use in the model as replacement for Philip's relationship.
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».