rename the tend and use init_timestep

components/eamxx/src/diagnostics/CMakeLists.txt

@@ -20,7 +20,7 @@ set(DIAGNOSTIC_SRCS
   aodvis.cpp
   number_path.cpp
   aerocom_cld.cpp
-  atm_tend.cpp
+  atm_backtend.cpp
 )
 
 add_library(diagnostics ${DIAGNOSTIC_SRCS})

components/eamxx/src/diagnostics/atm_tend.cpp → components/eamxx/src/diagnostics/atm_backtend.cpp

@@ -1,46 +1,47 @@
-#include "diagnostics/atm_tend.hpp"
+#include "diagnostics/atm_backtend.hpp"
 
 #include <ekat/kokkos/ekat_kokkos_utils.hpp>
 
 #include "share/util/scream_universal_constants.hpp"
 
 namespace scream {
 
-AtmTendDiag::AtmTendDiag(const ekat::Comm &comm,
-                         const ekat::ParameterList &params)
+AtmBackTendDiag::AtmBackTendDiag(const ekat::Comm &comm,
+                                 const ekat::ParameterList &params)
     : AtmosphereDiagnostic(comm, params) {
-  EKAT_REQUIRE_MSG(params.isParameter("Field Name"),
-                   "Error! AtmTendDiag requires 'Field Name' in its "
+  EKAT_REQUIRE_MSG(params.isParameter("Tendency Name"),
+                   "Error! AtmBackTendDiag requires 'Tendency Name' in its "
                    "input parameters.\n");
 
-  m_name = m_params.get<std::string>("Field Name");
+  m_name = m_params.get<std::string>("Tendency Name");
 }
 
-std::string AtmTendDiag::name() const { return m_name + "_atm_tend"; }
+std::string AtmBackTendDiag::name() const { return m_name + "_atm_tend"; }
 
-void AtmTendDiag::set_grids(
+void AtmBackTendDiag::set_grids(
     const std::shared_ptr<const GridsManager> grids_manager) {
   using namespace ekat::units;
 
   const auto &gname = m_params.get<std::string>("grid_name");
   add_field<Required>(m_name, gname);
 }
 
-void AtmTendDiag::initialize_impl(const RunType /*run_type*/) {
+void AtmBackTendDiag::initialize_impl(const RunType /*run_type*/) {
   const auto &f   = get_field_in(m_name);
   const auto &fid = f.get_header().get_identifier();
   const auto &gn  = fid.get_grid_name();
 
   // Sanity checks
   using namespace ShortFieldTagsNames;
   const auto &layout = fid.get_layout();
-  EKAT_REQUIRE_MSG(f.data_type() == DataType::RealType,
-                   "Error! AtmTendDiag only supports Real data type field.\n"
-                   " - field name: " +
-                       fid.name() +
-                       "\n"
-                       " - field data type: " +
-                       e2str(f.data_type()) + "\n");
+  EKAT_REQUIRE_MSG(
+      f.data_type() == DataType::RealType,
+      "Error! AtmBackTendDiag only supports Real data type field.\n"
+      " - field name: " +
+          fid.name() +
+          "\n"
+          " - field data type: " +
+          e2str(f.data_type()) + "\n");
 
   using namespace ekat::units;
   // The units are the same except per second
@@ -57,7 +58,14 @@ void AtmTendDiag::initialize_impl(const RunType /*run_type*/) {
   m_f_prev = Field(prev_fid);
   m_f_prev.allocate_view();
 }
-void AtmTendDiag::compute_diagnostic_impl() {
+
+void AtmBackTendDiag::init_timestep(const util::TimeStamp &start_of_step) {
+  m_start_t   = start_of_step;
+  auto f_curr = get_field_in(m_name);
+  m_f_prev.deep_copy(f_curr);
+}
+
+void AtmBackTendDiag::compute_diagnostic_impl() {
   Real var_fill_value = constants::DefaultFillValue<Real>().value;
   std::int64_t dt;
 

components/eamxx/src/diagnostics/atm_backtend.hpp

@@ -0,0 +1,53 @@
+#ifndef EAMXX_ATM_BACKTEND_DIAG_HPP
+#define EAMXX_ATM_BACKTEND_DIAG_HPP
+
+#include "share/atm_process/atmosphere_diagnostic.hpp"
+#include "share/util/scream_time_stamp.hpp"
+
+namespace scream {
+
+/*
+ * This diagnostic will back out the atmosphere tendency of a given field.
+ */
+
+class AtmBackTendDiag : public AtmosphereDiagnostic {
+ public:
+  // Constructors
+  AtmBackTendDiag(const ekat::Comm &comm, const ekat::ParameterList &params);
+
+  // The name of the diagnostic
+  std::string name() const;
+
+  // Set the grid
+  void set_grids(const std::shared_ptr<const GridsManager> grids_manager);
+
+ protected:
+#ifdef KOKKOS_ENABLE_CUDA
+ public:
+#endif
+  void compute_diagnostic_impl();
+
+  // Let's override the init time step method
+  void init_timestep(const util::TimeStamp &start_of_step) override;
+
+  // Let's override the initialize method to set the fields below
+  void initialize_impl(const RunType /*run_type*/) override;
+
+  // Keep track of field dimensions
+  int m_num_cols;
+  int m_num_levs;
+
+  // The tendency of what?
+  std::string m_name;
+
+  // Store the previous field
+  Field m_f_prev;
+
+  // Store the timestamp of the start of the timestep
+  util::TimeStamp m_start_t;
+
+};  // class AtmBackTendDiag
+
+}  // namespace scream
+
+#endif  // EAMXX_ATM_BACKTEND_DIAG_HPP

components/eamxx/src/diagnostics/register_diagnostics.hpp

@@ -23,7 +23,7 @@
 #include "diagnostics/aodvis.hpp"
 #include "diagnostics/number_path.hpp"
 #include "diagnostics/aerocom_cld.hpp"
-#include "diagnostics/atm_tend.hpp"
+#include "diagnostics/atm_backtend.hpp"
 
 namespace scream {
 
@@ -54,7 +54,7 @@ inline void register_diagnostics () {
   diag_factory.register_product("AerosolOpticalDepth550nm",&create_atmosphere_diagnostic<AODVis>);
   diag_factory.register_product("NumberPath",&create_atmosphere_diagnostic<NumberPathDiagnostic>);
   diag_factory.register_product("AeroComCld",&create_atmosphere_diagnostic<AeroComCld>);
-  diag_factory.register_product("AtmTendDiag",&create_atmosphere_diagnostic<AtmTendDiag>);
+  diag_factory.register_product("AtmBackTendDiag",&create_atmosphere_diagnostic<AtmBackTendDiag>);
 }
 
 } // namespace scream

components/eamxx/src/diagnostics/tests/CMakeLists.txt

@@ -72,6 +72,6 @@ if (NOT SCREAM_ONLY_GENERATE_BASELINES)
   CreateDiagTest(aerocom_cld "aerocom_cld_test.cpp")
 
   # Test atm_tend
-  CreateDiagTest(atm_tend "atm_tend_test.cpp")
+  CreateDiagTest(atm_backtend "atm_backtend_test.cpp")
 
 endif()

components/eamxx/src/diagnostics/tests/atm_tend_test.cpp → components/eamxx/src/diagnostics/tests/atm_backtend_test.cpp

@@ -26,7 +26,7 @@ std::shared_ptr<GridsManager> create_gm(const ekat::Comm &comm, const int ncols,
   return gm;
 }
 
-TEST_CASE("atm_tend") {
+TEST_CASE("atm_backtend") {
   using namespace ShortFieldTagsNames;
   using namespace ekat::units;
 
@@ -37,8 +37,8 @@ TEST_CASE("atm_tend") {
   util::TimeStamp t0({2024, 1, 1}, {0, 0, 0});
 
   // Create a grids manager - single column for these tests
-  constexpr int nlevs = 25;
-  const int ngcols    = 25 * comm.size();
+  constexpr int nlevs = 7;
+  const int ngcols    = 2 * comm.size();
 
   auto gm   = create_gm(comm, ngcols, nlevs);
   auto grid = gm->get_grid("Physics");
@@ -62,8 +62,8 @@ TEST_CASE("atm_tend") {
   register_diagnostics();
 
   ekat::ParameterList params;
-  REQUIRE_THROWS(
-      diag_factory.create("AtmTendDiag", comm, params));  // No 'Field Name'
+  REQUIRE_THROWS(diag_factory.create("AtmBackTendDiag", comm,
+                                     params));  // No 'Tendency Name'
 
   Real var_fill_value = constants::DefaultFillValue<Real>().value;
 
@@ -73,8 +73,8 @@ TEST_CASE("atm_tend") {
 
   // Create and set up the diagnostic
   params.set("grid_name", grid->name());
-  params.set<std::string>("Field Name", "qc");
-  auto diag = diag_factory.create("AtmTendDiag", comm, params);
+  params.set<std::string>("Tendency Name", "qc");
+  auto diag = diag_factory.create("AtmBackTendDiag", comm, params);
   diag->set_grids(gm);
   diag->set_required_field(qc);
   diag->initialize(t0, RunType::Initial);

components/eamxx/src/share/io/scorpio_output.cpp

@@ -1377,13 +1377,13 @@ AtmosphereOutput::create_diagnostic (const std::string& diag_field_name) {
     diag_name = "VaporFlux";
     // split will return the list [X, ''], with X being whatever is before 'VapFlux'
     params.set<std::string>("Wind Component",ekat::split(diag_field_name,"VapFlux").front());
-  } else if (diag_field_name.find("_atm_tend")!=std::string::npos) {
-    diag_name = "AtmTendDiag";
+  } else if (diag_field_name.find("_atm_backtend")!=std::string::npos) {
+    diag_name = "AtmBackTendDiag";
     // TODO: not sure if this is needed? Can skip, but what to do inside diag?
     // Set the grid_name
     params.set("grid_name",get_field_manager("sim")->get_grid()->name());
     // split will return [X, ''], with X being whatever is before '_atm_tend'
-    params.set<std::string>("Tend Name",ekat::split(diag_field_name,"_atm_tend").front());
+    params.set<std::string>("Tendency Name",ekat::split(diag_field_name,"_atm_backtend").front());
   } else if (diag_field_name=="PotentialTemperature" or
              diag_field_name=="LiqPotentialTemperature") {
     diag_name = "PotentialTemperature";