Testing the α and β methods of estimating evaporation from bare and vegetated surfaces in class
Bibliographic record
Abstract
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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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".